Chinertown
Other Resources => Component Deals & Selection => Topic started by: JohnnyNT on January 09, 2015, 05:55:25 AM
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I wanted to share some thoughts on the thing I've been long thinking about, something which would help me when I finally get to build my own chiner.
One can argue about superiority of one standard or another, the way I see it:
BB30/PF30
+ lower Q-factor available (no BB housing, shorter spindle)
+ often a tad lighter
+ 30 mm spindle stiffer
- creaks in the BB are very hard to get rid off, can't replace the BB housing itself (BB30)
- pressed connection less reliable in general threaded
BSA
+ threaded BB - more reliable and easily replacable
+ larger spacing between bearings - stiffer system
- only 24 mm spindle in most systems
- usually a bit heavier
I began wondering if there is a possibility of merging these two systems to have stiff and light crank with 30mm spindle and the replaceable and easy to maintain threaded BB.
It seems that some big players had the same idea recently:
Rotor (http://"http://www.rotorbikeusa.com/products/bsa_bottom_bracket.html")
Race face (http://"http://www.raceface.com/components/bottom-brackets/cinch-bb/cinch-bsa30/")
Unfortunately, these parts are priced pretty steep and I dwelled upon the idea of developing a more affordable alternative for 1x10/11 systems.
As far as I know SRAM BB30 cranks come in 2 spindle lengths:
(http://www.ruotapiu.it/wp-content/uploads/2014/11/BB30_Long_vs_Short_Spindle_v2_1024x1024.jpg)
One can see that 6.5 mm difference in spindle length corresponds to 6.3mm difference in spacer width, so far so good.
For both BSA and BB30 (MTB) the BB shell width is 73mm. Substracting it together with the spacer width from the indicated length leaves about 13mm for DS arm installation (it could be less, that's why the 6mm wide counter ring is for).
I considered the case, let's take the long spindle version of the crank, get rid of the spacer and get rid of the counter ring. You get 101.5(spindle)+6(counter)-73(bb shell)-13(DS arm)= 21.5 mm of free space (or more if DS arm doesn't need full 13mm). Seems enough to fit the BSA30 bracket there (10.75 mm for each housing, bearings themselves are 7mm each).
In fact a guy on MTBR performed such conversion with the shorter spindle XX1 crank and narrower (old) 68mm shell:
MTBR (http://"http://forums.mtbr.com/sram/xx1-bb30-crank-68mm-bsa-bottom-bracket-880184.html")
I asked him for clarification and he is convinced that idea above should work for a standard frame and longer spindle as well.
Two issues possible issues can occur, however both can be countered IMO:
- there is some space left and without counter ring there is sideways play in the crank (I think it can be corrected with (wave) washers, as it shouldn't be more than 2-3 mm)
- chainline could broken (this one is more complex, however from the DS point of view the ~10mm bb housing now acts as a spacer. That's less than 1mm difference compared to the spacer used in the shorter spindle. Therefore, any spiderless NW ring or spider for more 2x/3x setups designed to work with short spindle should work here as well)
That's it. Unfortunately it's just theory crafting on my part as at the moment I have no means of testing such setup. Perspective of using even BB30 x9/X0 with NW chainring on BSA frame is very tempting though.
Any input/thoughts appreciated. Of course if anybody here has a friendly LBS who would like to put this theory to the test, I'd be great.
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Nice analysis of the BB30 system.
I really have no input other than when I selected my BSA BB for both my bikes, my number one priority was reliability and easy maintenance. BSA fit the bill since the bearings are external so they can be as large as possible, and the threads make installation and removal very easy for maintenance. Also, most any crank brand sold today supports BSA, Shimano XT/XTR, SRAM XX1, Raceface, etc. I wanted to keep things simple, so I went with BSA.
Second priority was Q-factor, SRAM XX1 gave me the choice of Q156 or Q168, I chose the larger 168Q to ensure I would have good clearance between the crank arm and chainstays. Everyone wants shorter chainstays and room for fatter tires so designers have little choice but to push out the chainstays which leaves less and less clearance for the crank arms and chainring. I did lots of research and found that a narrow Q-factor wasn't a high priority for me, I do not have narrow hips and like the extra stability I get from the wider choice of Q-factor.
Lastly, chain line. I trusted that the SRAM BSA BB, SRAM 1x11 drivetrain, and XD hub provided a decent chain line. So far I've not had any issues related to the alignment of the chain. I get good, crisp shifting through all the gears.
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Yeah, reliability and ease of maintenance together with universality makes BSA a very solid choice. Still, if I could get benefits of both systems, why not to try ;) Not to mention that SRAM GXP BBs do not have the best opinion in the world, so I'd like to avoid them if possible (yes, there are counterparts from Aerozine etc. if needed).
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i used bsa, gxp, pf30 and now bb30 (and some older crazy standards). Used bsa on bsa frame. BSA on pf30 frame, pf30 on pf30, a lot of combinations... used a couple of rotor adapters ;D Now i'm going for a BB30 BB30 combination for the 1st time, i guess the one that gives more problems so i heard, but i am not a heavy guy so it should help. Never encountered any problem to date. By experience bearings last longer on BSA/GXP because they are better encased and protected.
it's really a pain to install BB/PF because you need more tools, i still don't have them. At least 2 kind of pricey. I still have tools for older standards that no one uses any more ;D ;D ;D
BB/PF has the advantage that it can use every crankset available, just get an adapter. 24mm frames can only use 24mm cranksets. Also there is less 30mm bikes in the market compared to 24mm, and you get better deals, imagine someone changes a bike from 30mm to 24mm and has to sell it, less people to grab it and prices drop.
when mounting always follow the instructions, they tell you what washers to use and how many ;) Respect it to get the best chain line.
BB/PF allow to assemble bikes with better chain lines and the lower q factor is something i really enjoy.
some very usefull video
https://www.youtube.com/watch?v=AftPKuX_tyo&list=FL43OKwkC8V5KMq2zDLYbwNw&index=28
i'm still using BSA on BSA on a road bike, no reason in particular, the bike i wanted (merida) come that way.
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BB/PF has the advantage that it can use every crankset available, just get an adapter. 24mm frames can only use 24mm cranksets.
What do you mean by "24mm frame" ? Any frame can fit basically any crank based on 2 prerequisites: (a) you have a proper BB insert (b) crank spindle is long enough . If these two are fulfilled, then even a frame typically specified for 24mm cranks (bsa,bb92 etc) can accept a 30 mm crank. That is basically what I outlined in my opening post. Of course issues with chainline and QF remain, but it's a separate problem.
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this can be a real stupid question but how can you put a 30mm crankset on a 24mm frame? :o
i at least had the idea it is not possible, truth be told never tried.
PS: not trying to be funny, i really had the idea it was not possible. ;)
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Like I said, I believe there is no such thing as "24 frame" per se. If you consider BSA for example, it has 34.8mm inner shell diameter. Even with 30 mm spindle it leaves 4.8 mm for threading in outer BB. And in these outer BBs you can have any diameter of bearings. Chech Rotor and Race Face links in the opening post, they do exactly that. I was just wondering if it can be done with Sram cranksets and that's the main purpose of this topic.
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ok, thrusting you, those 4.8mm seem small, the inside is threaded and cannot receive the bearing without some adapter. To have external bearings it does not work, all you have to do is see the manual for sram x0 or xx BB/PF assembly and you clearly understand this, believe me i have one, there is no way i can see
One one side you could always remove the washer you see in your photo (and they depend on the type of frame) on the other side there is no way, not even removing those adjusters you see on the top near the crank itself
homemade solutions you add to be a lot "macgyver" on the crank to get it centered. ;D
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I do not know how to convince you anymore. Yes, the solution needs external bearing and therefore longer crank spindle. The guy on MTBR uses it without a problem on 5mm shorter spindle and 5mm thinner frame than usual, so I see no reason why it should work with longer ones. Big companies are getting this solution to work as well. I've seen working solutions for Cannodale 30mm cranks on BSA frames too.
If it was impossible, manufacturers wouldn't bother making BBs like that: http://r2-bike.com/30mm-Crank-Spindle__BSA_1
Maybe I should make a drawing in CAD as well to make it more understandable....
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Hope also make a BSA 30mm BB. However based on your figures the long spindle might be 2.5mm too short. To be fair though they do not specifically mention SRAM cranks.
http://cdn.hopetechnology.netdna-cdn.com/wp-content/uploads/2014/03/BB-Selection-Table_Iss-4_01-2015.pdf (http://cdn.hopetechnology.netdna-cdn.com/wp-content/uploads/2014/03/BB-Selection-Table_Iss-4_01-2015.pdf)
However I suspect their new crankset will address your needs; at a price
http://www.bikeradar.com/mtb/news/article/hope-crankset-first-look-43427/ (http://www.bikeradar.com/mtb/news/article/hope-crankset-first-look-43427/)
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Good find ;) Their set include 2.5mm spacer, removing it would result in 94mm diameter of the whole BB which should be just enough for Sram as well ;)
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i did not said it was impossible, just i did not see how ;)
guess i was wrong.
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Arraider,
BB30 doesn't need special tools.... a bolt and some washers(how to vids out there)
BB30 is similar to BMX - pressed in bearing...and kids are doing bearings quite regularly(look for videos)
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Some time have passed, I have gathered all the parts and I can confirm that BB30 crank works on BSA frame. Parts used:
- Sram S2200 crankset with long spindle
- Rotor BSA30 Bottom Bracket + 2.5 mm shimano spacer on drive side
- Garbaruk oval 34T spiderless narrow-wide ring
(http://i.imgur.com/lW9a3Y9.jpg)
(http://imgur.com/K66fGh5.jpg)
Will put the full bike build in few days ;)
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Some time have passed, I have gathered all the parts and I can confirm that BB30 crank works on BSA frame. Parts used:
- Sram S2200 crankset with long spindle
- Rotor BSA30 Bottom Bracket + 2.5 mm shimano spacer on drive side
- Garbaruk oval 34T spiderless narrow-wide ring
(http://i.imgur.com/lW9a3Y9.jpg)
(http://imgur.com/K66fGh5.jpg)
Will put the full bike build in few days ;)
Great, so the long spindle of the S2200 has the exact same length as in your first post?
I am thinking on the same as I have BSA30 BB in my bike already and I want to replace my 170mm RF crank with a 175mm.
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Yes, it's like in the first post. I think that on Wolftooth page there is a diagram which cranks have long and which have short spindle somewhere.
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Hello JohnnyNT, I'm trying to do the same thing you did with an xx1 eagle and the same rotor bottom bracket you used. The Problem is that the cranks don't turn smoothly anymore as soon as I tighten them on to the bottom bracket. I guess it's because there's some sideways pressure from the cranks on the bearings which prevents them from turning. Did you use any of those drive side axle spacers that are shown on the picture of your first post?
Thanks!
Peter
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Did you try with different spacer widths ?
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yes I tried all possible combinations. If I don't put any spacers between the bottom bracket and the frame (so there's a small gap between the DS Crank arm and the bottom bracket) I can tighten it and everything turns smoothly. But when I put in a spacer on the DS (1x 2,5mm) to close the gap (so there's no sideyways movement in the crank) the cranks can't rotate freely anymore. My guess is that it's because the DS crank arm is pressing against the bearing and preventing it to turn. Maybe that's what those sram axle spacers are for? It looks like they would push against the metall inner ring of the bearing instead against the whole bearing?
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The bearings need a light preload, to avoid any play but just before feeling a drag.
Did you put the preload collar(a plastic ring) on the non-drive side of the crank to its minimum?
Or haven't you put one of the shims that come with the crank but shouldn't in your case?
Do you have 49mm for the chainline(horizontal distance between the center of the seat tube to the ring )?
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I didn't put in the preload adjuster because otherwise the crank axle would be too short. I think JohnnyNT did the same thing, that's why I'm wondering how he got it to work...
what do you mean by "shims" ? do you mean the spacers? I tried many different options but none worked...
You said that the bearings need a light preload to avoid play but just before feeling a drag....but how does it work with other cranksets that don't have that preload adjuster? On all of my cranks until now i just tightened them to the according torque and used spacers to avoid any sideways play. Besides I'm already feeling drag even if the DS arm is screwed on very lightly, I guess that would be way to loose even if I could use the preload adjuster to eleminate play
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I'm not sure about the chainline, will have to check for that. I was more concerned about getting the cranks to turn freely first...
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Hi Peet182,
I was encountering similar problems as you do (crank not moving in smooth manner) at first, I put a very narrow (don't really remember the thickness right now, around 1 mm ) spacer on the drive side between BB and crank and it solved the problem. Axle is still long enough to hold everything together.
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Hi! Thanks a lot, that was exactly the information I was looking for! Could you maybe tell me where you got the spacer? Is it just something from the warehouse or some specific spacer for bikes? I'm having a kinda hard time to find a spacer like that around here...thanks!
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Your best bet would be asking at a lokal bikeshop. Usually they have plenty of spacers lying around.
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Or wheels mfg
http://wheelsmfg.com/crank-spindle-spacers.html
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perfect, thanks a lot for the help! I will try to get some of these and get it to work!