Weight Weenies

Hi guys,

I need your help. I have a Zipp Vumaquad crankset on my current frame. I am considering buying a new frame which would come with Pressfit 86.5 standard. There is no bottom bracket available from Zipp which allows the use of Vumaquads on a Pressfit 86.5 frame.

I have found some old threads
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which recommend bearings/adapters from Rotor and THM Carbones.

While I found one comment which said the Rotor 4130 bearings did not work, there is no confirmation that the THM adapter works, or does not work. Any experience out there, please? PLEASE !!!

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I am currently looking at 4 bearings for the combination of Zipp Vumaquad cranks in a Pressfit 86.5 frame:
Rotor 4130 (the name says what the above combination requires: an outside diameter (OD) of 41mm and an inner diameter (ID) of 30mm to accommodate the 30mm spindle)
THM Carbones
Tune Smart Foot PressFit BB92 & BB86 Kit MTB + Road (these use the THM bearings, apparently)
BOR ROAD Bearing Kit BB86

I think you could add the Race Face cinch BB for BB92 to your list. That one has the nice advantage of integrating the cup into the outer race allowing them to use larger ball bearings (should boost longevity).

I saw in that other thread someone saying they couldn't get it to work and that they thought the crank axle wasn't long enough and was leading to the crank binding (side-loading the bearings) when tightened. I guess I don't see why that should be the case since the crank is compatible with italian 70mm shells with the same thickness external BB cups as with a 68mm. When running the Italian setup you leave out two 1mm spacers that you use on the BSA. Anyway, point being that the crank seems to have an extra 2mm of room to play with... compared to a BSA or BB86 setup.

I think the Rotor 4130 bb will work but I have no experience with that, but it does have the 41mm od and 30mm ID that is need.

I think the issue might be more with the length of the axle, I tried fitting my Vuma Quads to a frame with a BB386evo bottom bracket, the vuma axle was too short, resulting in binding when trying to tighten the crank bolt up enough, I even took out all the spacers and that did not work.

It might work if I took out the bearing seals, but that would leave the bearings completely exposed.

lannes wrote:Are you trying to fit vumaquads to a frame with a bb386evo bottom bracket ?

If you are it doesn't work, I've tried it the quads axle is too short.

This might help with the frame bb standards

http://problemsolversbike.com/files/tec ... erence.pdf

i am trying (or was going to try) to fit vumaquads to a Pressfit 86.5 bottom bracket. if i understand correctly, BB386evo shell width is 86.5, same goes for Pressfit 86.5, only difference is the shell diameter (BB386evo = 46, Pressfit 86.5 = 41). so, if you say the axle is too short for BB386evo, this has to be true for Pressfit 86.5 too...

the vumaquad spindle is 101mm long. but i do not know if that includes the part of the spindle that inserts into the crank arms though. reading through the links below, i would say it includes the part that inserts into the crank arm (see this pic, which shows the BB90 shell = 90mm with bearings sticking out 2mm on each side = 4mm)

also interesting:
zipp vumaquad + BB90 part 1
zipp vumaquad + BB90 part 2

Maybe you can ask Zipp directly, they might have tried to do what you want as part of in house testing.

Zipp said that the VumaQuad was not designed and has not been tested to work with press fit BB or alternative bearings. And they do not recommend to make this alteration as there is an increased safety risk.

Alright... This doesn't bring me any further (even though their reply came quickly; that's what I call customer support!)...

I just measured some parts I have laying around here. The axle length from inside edge to edge when torqued on a vumaquad is about 88-89mm (sorry I dont have calipers that wide, just used tape measure. The portion of a ROTOR bb4130 BB cup which extends past the frame is 2.1mm per side. ( I mic'd that, so thats right) In theory that would leave you with a minimum BB width of 90.7mm. I just confirmed this on my TCR with rotor 3df cranks and bb4130bb. Removing seals wouldnt work, as they do not protrude beyond the inner bearing race.

I havent looked in awhile, but if memory serves, THM had a 41mmx30mm BB that may be narrow enough.

thank you!

the rotor bearings are the cheapest solution (approx. EUR 40.-) but that won't help if those are to wide...

the BOR bearings should be 11mm wide ("special bearings 30x41x11") but i do not know how much of those 11mm stand out of the frame, and how much is inside... on the other hand, BOR also states on their website "Special BB30/BB905 in 30x41*x7"

THM bearings are 11mm wide, THM confirmed this to me.

I think the problem is that most of these conversion BBs have external lips like the rotor 4130 to hold the bearings in place against the cup, as there is no internal stop in the cup (at least not in my TCR (pf86)) this lip is probably causing too much distance from face to face, ie the quoted 90.7mm for the 86bb plus two bearing lips. This is almost certainly too long for most 30mm spindles. It *think* its only bb386 cranks and rotor spindles which have enough spare interface to allow this usage. My vuma cronos come out at about 88-89 mm too as 743power mentioned, so probably too short by ~3mm.
Perhaps the problem could be solved with headset bearings like these 41x30.2x6.5 probably need to use two either side to prevent early failure with such small bearings and perhaps a internal plastic spacer to prevent inward bearing creep? http://www.chainreactioncycles.com/cane ... -prod11266

i measured my current vumaquad crankset w. BSA bearing cups yesterday: 86-87mm from outside cup to outside cup.

so, i would guess if there are Pressfit 86 bearings which flush-fit into the BB shell (not sticking out of the BB shell, i mean), then i think it would work. don't you think so?

+1 on machinenoise's post - Without some sort of bearing cup lip, how would they stay in place, the rotor 4130 lip looks to be around 1.5-2mm

lannes wrote:+1 on machinenoise's post - Without some sort of bearing cup lip, how would they stay in place, the rotor 4130 lip looks to be around 1.5-2mm

i don't know, i am no engineer with only limited understanding of technology , but maybe with a machined tube in the correct length? my assumption would be based on the fact that there are no elevations inside the BB shell. in the case of Pressfit 86.5 the BB shell is 86.5mm wide. with an assumed 10mm of bearing width on each side, the tube would have to be 66.5mm long... then no "lip" would stand out of the BB shell... no?

but i begin to think that it would be better/easier to buy a THM Clavicula/Clavicula M3/Storck Powerarms crankset instead. those do work and there is no DIY involved...

What about the FSA BB86 -- BB386EVO adapter? From the image below, this appears to be a 'flange less' design, allowing the center sleeve which appears to provide spacing could probably be machined to afford slightly narrower spacing thus affording more clearance:

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I think this has a lip as well:







here's some info on that product. apparently it has been developped with Giant...