Phil Wood-y Bottom Bracket

Shimano Bottom Brackets–Phil Wood Style

Nota bene:
Since the original composition of this page, Shimano has replaced the UN72 bottom bracket with a revised (UN73) design, which (like the UN52 mentioned in this article (a.k.a. the current UN53)) does not have a removable mounting ring on the right side, but rather has the threads integrated into the shell (see pictures below). No problem! These bottom brackets can still be modified as discussed in this article per the UN52-specific information. UN72’s still turn up on ebay and in smaller shops, so I have left information on that model in situ. The only downside with the new UN73 design is that (unlike the UN72), the UN73 cannot have its cups removed and remaining cartridge unit paired with Phil Wood mounting rings threaded to “rare,” non-I.S.O. sizes (e.g. Raleigh (26 t.p.i.), Italian (wider shell, larger cup), French (both sides=right threads), or Swiss (both sides=left threads). If you have an older Raleigh with 26 t.p.i. threads, you can have a bike shop retap your bottom bracket shell to I.S.O. 24 t.p.i. and use common I.S.O. parts.

Secundum nota bene: By 19 April, 2007 Shimano discontinued the UN53 and UN73 bottom brackets and replaced them with the (according to Cambria Bikes) UN54 and UN74 models. No significant changes have been made (except some UN74’s have plastic mounting rings on the left side (The UN73’s had a metal ring). Rant alert: Given the fact that Shimano bottom brackets have stickers placed on the cartridge body post fabricatum, I can’t help but wonder whether this “new” model is the company’s attempt to recategorize current in-house inventory for tax purposes. Moreover, It is not going unnoticed that Shimano’s use of plastic parts has been moving up their heirarchy. Today’s UN74, with its integrated shell threading, plastic cup (and even hollow spindle) is the same bottom bracket as the UN52 units of years past (which was inferior to the UN72)–and some UN52’s had a metal left mounting cup! (conclude rant).

Intro:
Traditional cup-and-cone bottom brackets are great (though, as of 2007, increasingly scarce), but equally great, more durable and maintenance free are Shimano (or Sugino, Nashbar, FSA, etc.) cartridge bottom brackets. With the Shimano unit, all you have to do is identify the proper spindle length you need, pop one in with a ratchet-wrench mounted tool, and ride worry-free for thousands of miles. No pin tools, no spanners, no lockrings, no frequent fine-tuning adjustments or tear-downs for regreasing. Even if (as some might claim, though I have never seen it) a Shimano cartridge unit blows up earlier than, say, a high-end Phil Wood “crank axle” (a.k.a. Gucci-speak for “cartridge bottom bracket,” you can buy at least four Shimano UN73’s for the price of one Phil Wood, and probably seven UN53’s (which have a solid spindle, (usually) a plastic cup on the left side, but the same bearings as a UN73) for the same price. Despite the ne plus ultra status of Phil Wood crank axles, it is unlikely that more than two Shimano bottom brackets will poop-out before one Phil Wood (By the way, John S. Allen has a Raleigh Twenty on its third Phil Wood bottom bracket, so Phil units are not completely, as the industry likes to say, “bomb proof.” It is worth noting, however, that John Allen is not your average cyclist).
But there may be times when a Phil Wood bottom bracket might seem a better fit for your application than an off-the-shelf Shimano. For instance, if you want to obtain two-sided chainline adjustment (to keep your bikes “Q” factor down by using the shortest possible bottom bracket spindle length, or to compensate for an offset chainline after you upgrade or swap out parts), you may want a Phil Wood crank axle. Or if your bike has an unusually wide bottom bracket shell (as on a vintage Raleigh Twenty, with its 76mm (vs. 68mm standard) wide bottom bracket shell), you may want a Phil Wood unit, for Phil Wood’s mounting rings do not have shoulders, and allow a custom fit unobtainable by the standard-width, single-shouldered, Shimano units.

Not so! It’s easy to replicate the features of a Phil Wood bottom bracket by grinding the shoulder off a Shimano UN52, UN53, UN72, or UN73. The UN72 (now discontinued) even has two removable mounting rings–just like a Phil Wood (the “adjustable” mounting ring has no shoulder and is unattached when you buy the unit; the fixed mounting ring (with the shoulder) may be removed by placing the bottom bracket in a pipe vice and removed with a punch) The UN52/3’s and UN73’s, by contrast, have an integrally threaded and shouldered (right) mounting side and an adjustable (left) side, and therefore only the adjustable (left) side is removable. Still, any of these models may be modified with little fuss.

But why modify a Shimano bottom bracket instead of buying a Phil Wood? Cost! Do the math. Or, if you have a wad of cash in your pocket, just buy the Phil Wood crank axle and go surf somewhere else. The math follows:

Phil Wood option:

Phil Wood “crank axle” ($109.00), Phil Wood lockrings ($35.00 for ISO British; $40.00 for Raleigh 26 t.p.i.), Two (2) Phil -specific mounting tools ($30.00 for two consumer-grade tools). Harris Cyclery carries Phil Wood (et al.) here.

Shimano option:
UN53 ($25.00) or UN73 ($40.00), Park BBT-2 installation tool ($12.oo, or $24.00 if you want two), and, if you don’t own one, a bench grinder (circa $50.00).

Totals:
$174.00 for Phil Wood unit (more for specialty mounting rings) vs. $87.00 (for Shimano UN53 + one mounting tool & grinder (or $114.00 for UN73 + two mounting tools and grinder). If you have already have a grinder, subtract $50.00 from the Shimano option’s total cost ($37.00 to $64.00 total); and if you didn’t have a grinder, you now have one for your next modification(s). Believe me, you will find uses for it.

So then, how do I do it?

Phil Wood-y Shimano Cups

You will need:

  • a Shimano sealed cartridge bottom bracket (UN52/3/4, UN 73/4, or UN 72 bottom bracket, or whatever the corresponding numbers for these models are today (because I will tire of updates));
  • one or two Shimano bottom bracket installing wrench(es) (Park BBT-2); and
  • a bench grinder (don’t forget safety goggles + ear protection).

Note for Raleigh Twenty owners (unless you have a UN72):
If you are modifying a Raleigh Twenty, you must have the frame’s stock 26 t.p.i. shell tapped out to a standard English 24 tpi thread at your local bike shop, or find a UN72 (and pay an additional $70.00 through the nose for Phil Wood Raleigh 26 t.p.i. mounting rings and consumer grade tools). Assuming you are tapping out to I.S.O. 24 t.p.i., be sure to drive the taps in deep enough to accomodate the Shimano mounting rings, which are wider than the stock Twenty cups.

Pre-step for UN72 only:
(Really not necessary, and now somewhat obsolete) If you are modifying a UN72, and for some reason want both cups removed and/or loosened (either to use Phil mounting rings with the Shimano cartridge, or to use a Phil cartridge with Shimano rings), clamp the cartridge unit into the pipe vice part of a bench vice and use a punch to free the fixed cup. You may need to rap on the shoulder of the mounting ring, or on the inner part of the mounting ring itself to dislodge it. Regardless, take care not to damage the threads. Once you have freed the right side mounting ring, you must reseat it on the cartridge before you can continue with the modification.

Procedure for all models:
Put on your safety glasses and hearing protection, and turn on your bench grinder. Hold each end of the bottom bracket axle with one hand (two ends, two hands, just to clarify). Carefully touch the shouldered edge of the fixed side mounting ring to the grinder wheel. The cartridge should begin to spin quickly as you hold the axle ends–too quickly to actually grind off any metal. Now, use your thumb–the thumb holding the non-shouldered end–to slow the rotation of the cartridge just enough to allow the unit to spin and to remove metal from the lip. As long as the cartridge is spinning, the lip will wear away evenly. Do not, under any circumstances, let the threads touch the grinder wheel, or you may find yourself buying a replacement bottom bracket. When the shoulder has been ground flush with the cup, voila! You have a full-featured, Gucci Shimano cartridge bottom bracket allowing adjustable chainline or installation in a Raleigh Twenty.

Installation notes:
When you install the modified bottom bracket in the frame, screw in one cup fairly far (the left ring if you are modifying a UN52). Then slip the unit into the shell and tighten it. Back the left side mounting ring out a bit, and tighten the “fixed” (right) side until you have the desired allignment (the reason for all this back and forth is to get the bottom bracket to settle in both mounting cups before any real torque is applied. Misalignment can cross-thread the bottom bracket; and if you have a Raleigh Twenty, with an already-comprimised set of threads (retapped), you will be thoroughly bummed to have come so far only to trash your frame in the final step.

Written: 10-00
Last update: 04-07

Questions? Comments? Drop me some…
email

 

 

 

 

UN72 (discontinued)

UN73 (current model, like UN52 and UN53)

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12 Responses to “Phil Wood-y Bottom Bracket”

  1. josh Says:

    Excellent article! May I ask you to clarify one thing for me? I bought a pair of Phil Wood Mounting Rings and my Shimano UN72 does not quite slip in. I know this will sound stupid, but is that what the grinding is all about? The first time I read about using Phill Wood rings was over at Sheldon Brown’s site and he doesn’t mention any grinding necessary with the UN72. So, kudos to you for that!

  2. houseofyes Says:

    josh:
    The lip I talk about grinding off in my article is actually the right side “fixed” cup lip of the UN72 and UN73 models above. Removing this lip via grinding allows you to custom adjust chainline, or to upgrade irregular sized bottom bracket shells (as on a Raleigh Twenty) with modern parts. Now, on to the problem you mention. If you have a UN72 with both cups removed and your Phil rings won’t slip over the Shimano body, yes, you can remove material from the bottom bracket unit’s shell (via grinding, sanding, etc.). I would recommend this only as a last resort, and only if the fit is already quite close (you could use a caliper to determine that). If you remove too much material, you will create slop in your drivetrain. As far as a tight fit goes, it is not uncommon to remove the fixed (right) side of a UN72 only to have that same cup seem as though it does not want to slip back on (due to steel vs. aluminum’s response to room temperatures). To see how close your fit is, 1) try dabbing some oil on the unit where the rings go and using a wooden block and soft-head hammer to see if you can tap the rings on a bit, OR 2) put the unit in the freezer while warming the Shimano or Phil rings in a 200 degree oven. Wear gloves and try the wooden block + hammer trick to see if you can coax the rings on a little. Note: Bottom bracket bodies are well machined. If you can tap the rings on a little, then you will be able to seat them fully on the bike. Again, removal of material from the body of the unit is the least desirable option, and if you remove too much, you will be out some really good parts. That said, to remove material from the bottom bracket unit body, as with removing the right side lip on the just hold each side of the axle and use your thumb to control speed. Go slow and check the fit often (but remember, grinding the unit will heat it up and expand the steel, making it seem like the rings won’t fit. Finally, there is the possibility of bodily injury during this procedure, so please take appropriate safety measures. Thanks for your interest.

  3. josh Says:

    Thanks for the reply! I’m going to try the freezer/oven method and forgo the grinding. I still don’t understand why the two don’t just fit to begin with, seeing as I’ve never seen mention that this could be a problem. Makes me think I’ve got either bogus Phil rings or the wrong model Shimano with a UN72 sticker on it. However, if I have success with the freezer/oven method, I can’t think of a more ideal fit. Talk about zero slop . . .

  4. bruce Says:

    Good article! I’ve currently goat a Raleigh 20 project going, and my Shimano UN-71 would not fit into Phil 26 TPI rings as delivered either, just as josh reports. I opened up the rings on my lathe (took off next to nothing) and now they fit fine. I’m not so sure about the advisability of heating the rings / cooling the bearings to assemble the parts. When the temperatures have equalized the parts will be assembled very tightly. At least one of the rings has to be able to turn relative to the bearing housing in order to thread the assembly into the frame, and that may prove difficult.

  5. Ross Says:

    First off, thanks for the thoughtful and useful article. Grinding the shoulder off a drive-side Shimano BB mounting ring makes a lot of sense… Your article helped spur me to get back to working on the Twenty I’ve had for a few years.
    [House-of-Yes response Thanks. We need more R20’s on the road].

    Your explanations concerning French and Swiss BB thread standards are incorrect. French is 35 x 1mm RH thread, both sides. Swiss is the same, except with a LH thread drive-side.
    [House-of-Yes response: “No, I am not incorrect, you make assumptions based on the data I chose not to include. I only mention Swiss, French, and Italian bottom brackets as “non I.S.O.” in my article–and I only make “explanations” to the direction of the threading in reference to these particular parts. I do not make any claim as to the number of tpi in the shell. This is not because I don’t know them. If you have Swiss or French bb threads, don’t even bother with retapping them to ISO 24 t.p.i.. Only retap to 24 t.p.i. when you have an old Raleigh (with 26 t.p.i.) project, like, as this article is inclined toward, a Raleigh Twenty. I do not see how this oversight on your part and subsequent “critique” enhances my article or genuinely offers appreciation of my work. Still, I will leave this portion of your comment intact.
    And for the record, for those of you who want the full monty:
    French threaded bottom bracket: Right hand thread, 35mm x 1mm=1.378″ x 25.4 t.p.i.
    Swiss threaded bottom bracket: Left hand thread, 35mm x 1mm=1.378″ x 25.4 t.p.i.
    Italian specs: same as British, but with 70mm shell (British has 68).
    British/ISO: 1.370/1.375 x 24 t.p.i.

    For my Twenty, my initial plan was to use an old Shimano UN52/72 (or somesuch) with 26tpi Phil adaptor rings, to avoid dulling my BB taps for no good reason. (IIRC, Shimano and Phil BBs have the same diameter at the outer edge (30mm), and Phil rings fit similarly on a Shimano cartridge as a Phil (tight).) …However, the threads in the BB shell did not go deep enough to retain a Shimano cartridge. The shell is about 77.2mm wide. A Shimano cartridge is 57mm with the rings removed, across the outside of the bearings. (IIRC, 68 and 73mm Shimano BBs differ only in the offset that the drive-side adaptor ring provides. I don’t recall if the spindle is centered differently relative to the cartridge.) A Phil BB would not work, either, at 60mm wide.
    [House-of-Yes response: Your bottom bracket taps, provided they are shop grade, will do scores of retaps. I’ve done 6 Raleigh Twenty retaps + additional cutting (and countless other bottom bracket chasings), and my tools are going strong].

    So, I retapped the threads to 24tpi, and extended them about 3mm per side to allow standard English Phil rings to engage a Shimano cartridge. (Phil rings rather than modified Shimano because they require less thread depth, and thus less new thread cutting.)
    [House of Yes response: That’s why my article instructs tapping in further on the R20. As said, your taps will do more bikes than you will own. If you are a bona fide shop, you get wholesale taps and a tax write-off to replace them. Moreover, the cost-to-performance factor of the Phil rings is too high to warrant using them when there are other options. In my opinion, which is worth about as much as sand in Death Valley, Phil & Co. has been running a high-end marketing racket since the 1960’s. One motivating factor of this article is to educate people that they do not need gucci parts to update their Twenty].

    Woot, Twenty travel bike here I come! The Huffy tune-up is sweet, BTW.
    [House-of-Yes response: Thanks. Your comments are welcome and appreciated. But please, don’t say I am incorrect in my facts–You kinda tweaked my horns. If I inspired you to get back to work on your Twenty, please be courteous, not condescending. I wrote this page to do you, and others, a favor—as well as share my knowledge.].

    House-of-Yes final comment: if you think I need to be more specific in my facts, email me offline so I can reword things for the layman before you call my work “incorrect.”

    :]

    Ross

  6. tealaser Says:

    Great info on the UN-72 a la Raleigh Twenty. I have the “Twenty”, bottom bracket, and I just need to get the Phil cups. I was planning to use a propane torch to heat the pressed on cup to remove it from the housing. It seems like this might pose less risk of damage to the housing and/or the threads. I would like your thoughts or experience. Plus, from your procedure, I’m not quite sure if I understand the shoulder of the housing has to be ground. Would you elaborate a little more.

    Great stuff! Thanks.

  7. veloapocalypse Says:

    tealaser:

    Glad you like the page.
    With careful use of a punch, you can remove the right side “fixed” cup on a UN-72; or you can suspend it loosely between the jaws of a bench vice and punch the b.b. body away from the fixed cup side with a soft head, dead blow hammer (using wood to protect the spindle and a towel to catch the bb unit!!). No need to use the torch, really, but you can if you want. I’ve never damaged the housing of a UN72, or the threads.

    The shoulder needs to be ground down on the Shimano unit because the Shimano units have a shoulder built in on the right side–either on the right ring, or, if the right side is integral to the bb, which is the case on modern units, machined into the shell itself. To make a Shimano unit serve in lieu of a Phil unit and/or parts, this lip needs to go bye-bye. Moreover, Shimano units are made for a 68mm (or 72mm) shell The Twenty has a shell that is 78mm wide. Now, if you are using Phil rings in tandem with a Shimano unit that has two metal “lockrings” that have been removed, you do not need to do any grinding, as Phil rings have no lips. If, on the other hand, you grind your Shimano unit’s right side lip down to nil, you will not need to buy Phil rings. I’d suggest saving yourself some money and buying a cheap grinder instead of a pair of Phil rings. But that’s just me.

    Hope that helps.

    I assume that by “Twenty” bottom bracket, you mean “UN72,” or some sort of Shimano unit.

  8. WCBRISTER3 Says:

    I JUST BOUGHT A RALEIGH 20 ON EBAY, RIDDEN IT AND LIKED IT, BUT NOW THE BOTTOM BRACKET (ORIGINAL) HAS FAILED. I WOULD LIKE TO HAVE THE SHELL RE-TAPPED TO 24 TPI AND GO THE SHIMANO ROUTE YOU SO CLEARLY DESCRIBE. I SOMETIMES SEE UN-72 BBS ON EBAY BUT DON’T KNOW WHAT DIMENSIONS I NEED, IE. AXLE LENGTH AND BEARING LENGTH. SINCE A 76MM SHELL IS SO UNUSUAL IT MAY BE UNLIKELY TO FIND A DISCONTINUED UN-72 THAT IS APPROPRIATE. YOU WOULD BE DOING ME A GREAT SERVICE IF YOU COULD TELL ME THE EXACT SPECS OF THE BB/AXLE THAT I NEED AND WOULD BE REASONABLY ABLE TO FIND. I HAVE A BENCH GRINDER AND A DESIRE TO AVOID BUYING “GUCCI” BIKE PARTS. THANKS VERY MUCH FOR YOUR VERY LITERATE AND INSTRUCTIVE TREATISE; IT IS LIKE A RADAR SEEING THROUGH FOG. PERHAPS MY “20” WILL ROLL SOME MORE. ALL THE BEST, BILL BRISTER

  9. WCBRISTER3 Says:

    I JUST BOUGHT A RALEIGH 20 ON EBAY, RIDDEN IT AND LIKED IT, BUT NOW THE BOTTOM BRACKET (ORIGINAL) HAS FAILED. I WOULD LIKE TO HAVE THE SHELL RE-TAPPED TO 24 TPI AND GO THE SHIMANO ROUTE YOU SO CLEARLY DESCRIBE. I SOMETIMES SEE UN-72 BBS ON EBAY BUT DON’T KNOW WHAT DIMENSIONS I NEED, IE. AXLE LENGTH AND BEARING LENGTH. SINCE A 76MM SHELL IS SO UNUSUAL IT MAY BE UNLIKELY TO FIND A DISCONTINUED UN-72 THAT IS APPROPRIATE. YOU WOULD BE DOING ME A GREAT SERVICE IF YOU COULD TELL ME THE EXACT SPECS OF THE BB/AXLE THAT I NEED AND WOULD BE REASONABLY ABLE TO FIND. I HAVE A BENCH GRINDER AND A DESIRE TO AVOID BUYING “GUCCI” BIKE PARTS. THANKS VERY MUCH FOR YOUR VERY LITERATE AND INSTRUCTIVE TREATISE; IT IS LIKE A RADAR SEEING THROUGH FOG. PERHAPS MY “20″ WILL ROLL SOME MORE. ALL THE BEST, BILL BRISTER

  10. houseofyes Says:

    You have all you need. You don’t even need a UN72, since you have a bench grinder and can grind off the machined lip on the newer bb’s. You will, however, probably want to replace the cottered crank with something newer. The fact that the bb shell is wide is not a problem, because you are removing the built-in stops ( i.e., the lips). You may want two bb install tools to make sure you can hold one side while you tighten the other; or you can loosen one side as you tighten the other to adjust chainline.

    There is no simple answer to “which bb do I need,” because no one uses the same parts. For one Twenty, I used a 68mm shelled, 107mm spindle (the narrowest) UN72 with a mid 1990’s Shimano Ultegra 600 double crank (with inner chainring removed) I got from one of the deep discount shops. I used a Shimano Nexus 7 on the rear (and later a Sturmey 7, and am now back to the Nexus). Remember, you are taking off the lips of the bb via grinding, so you can adjust the chainline as far as the parts will let you–which is to say, the point at which the left crank arm touches the bb shell, or the right spider or chainring (or chainring bolts) does the same at the shell, or on the chainstay. That said, you will also want to look at overall symmetry (measure the distance between each of the crankarms and the chainstays and try to keep them somewhat equal). If you are heavily skewed to the right, you will need a longer bb just to compensate. No big deal. In fact, most cranks are not fully symmetrical from the factory, and no one seems to notice. There is also this thing called Q-factor (overall distance between the crank arms), which is another story I will refrain from talking about.

    I’d say if you are looking for a single ring setup and some sort of internal hub in the rear, get a 107 or 110 bb and go from there. As long as the lips you will be grinding down are metal, you are fine. You are not limited to Shimano. I was able to use my stock chain guard with my 107 spindle and Ultegra 600 cranks. Unless you want to grind the chain guard down to fit a 42mm chainring, find a 36mm chainring (I’d suggest the Sugino XD-600 with 26-36-46 rings). I will also say that this same 107mm bb was able to hold a quadruple chainring I set up with Sugino XD cranks (20-30-42-54)–I used the now-unavailable Avid “Microdapter” to add the fourth chainring. That mod was another story, and I did not keep it. It was more of an experimental thing.

    Know that some setups (like my Nexus) will require you to spread the rear triangle. There are pages on the web telling you how to do this, should you decide to go that route. If I were to reveal my specific method of how I have spread several of my old Raleigh frames, someone would call me a ham-fist. To my credit, they all have come out aligned and fine.

    And one of these days, I’ll have to get a video up.

  11. Brian Says:

    You wrote in one of your comments above that only raleigh threaded bottom brackets can be tapped to standard english 24 tpi x 1.37mm. I’ve had very good results tapping a swiss bb to english threading. The ‘Handedness’ of the threading is the same, and the .007″ difference in shell size is negligible. In fact, the swiss thread pitch is closer than raleigh threading to english, and I believe it resulted in a closer to perfect conversion. I just wanted to put this out there.

    The sex change for a french bb would have to be reaming, and tapping Italian, because of the drive side thread direction. Anything can be tapped italian (though it may have to be reamed first) because of the substantially larger shell size.

  12. Brian Says:

    Follow up:

    in fact, the Park tool website says this:

    “The common thread norm for the bottom bracket-bearing unit is 1.37” x 24 TPI. In some countries outside the USA, this is referred to as 35mm x 24 TPI. This is because the number 1.37″ has little meaning, and the term 35mm is common terminology.”

    and their chart shows bb shell inside diameter as equal at 33.6-33.9mm for all national standards but italian. see here: http://www.parktool.com/repair/readhowto.asp?id=97

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