BB30/PF30 chainsets - where?

munkster

Having got used to 170mm crank arms on my road bike I'm wondering whether the stock 175mm crank arms on my Boardman CX are the reason why it doesn't feel "quite right" (mainly ridden on road as a winter bike) so was looking into replacement chainsets. It's probably a princess-and-the-pea thing but if I can pick up a c/set "not much" it might be worth a shot.

It has a BB30 (same as PF30?) FSA double chainset with an Apex groupset but I can't seem to find any appropriate SRAM (or other) chainsets for under £100, say. Am I searching for the right thing?? Any help appreciated.

jgsi

BB30 and PF30 are close but not the same, so be careful.
If you having difficulty in getting a bb30 chainset for the right price may be think of a bb30 convertor - praxis or FSA threaded insert to allow for Hollowtech choices?

simonj

Many people say you can't tell the difference, but others say you can. If they're 175mm now I presume your bike is large or XL and you're 6'+. Do you have short legs for your height, 31" or shorter? If your legs aren't short are you sure you need 170mm cranks as could be an expensive change? SRAM Apex do not do BB30 cranks, so it's either go up to Rival, find an FSA (BB30 or BB386 with spacers ~ £8) or convert PF30 to BSA (~£20) and your choices open up - Shimano 105 crank + HT2 BB etc... Some may say going BSA may reduce to future issues with BB30/PF30 anyway. If it were me I'd check you definitely need 170mm cranks first. I do, but I know that because my legs are short for my height. If I build a bike I'll put on 170mm, but if I buy off the shelf I'd stick with 172.5/175 unless I just happened to have one in garage spare.

munkster

Bike is not a large, it's a medium AFAIK and I'm 5'10" and 170mm crank arms were recommended when I had a bike fit a few years ago... I do probably have shorter legs for my height however so do think 170mm makes for a better fit for me. Quite agree that if I can get away without the expense it would be good but despite fiddling around with the position etc I can't seem to get the feel of the pedalling action quite right. Like I say probably princess and the pea, will keep a look out for 2nd hand Rival then, cheers.

simonj

Same height as me then, I have 31" inside legs, so a bit short for my height and I go for 170mm cranks too. Didn't click on my legs were short for my height for a while. In the Boardman CX I thought the Medium came with 172.5mm cranks TBH so I'd double check what you have. My problem in having short legs, is that to get the stand over right I size down a bit to a medium, but then find it's a bit short in length, so I get a bit hunched in the middle and end up with seat right back and too much weight on my wrists. I now tend to go for compact geometry bikes or on CX's, if in the middle of sizes, tend to go for the larger rather than smaller, but then have the seat quite low.

munkster

I did check, I have both measured them and read with my own eyes the "175" on the back of the crank arms... Pretty conclusive!

What you describe in terms of position woes sound a bit familiar. You sure you haven't got a long lost twin you've never met? ;-)

simonj

Ha ha, dunno will ask my mum! Maybe they changed cranks specs at some point but the current silver specs on Boardmans site say 172.5 for a medium, most bikes I've bought TBH come with 172.5 or 175, but if I get chance I'll always swap to 170. I bought a few FSA SL-K cranks off ebay for a good price (~£125) and put them on new bikes when they arrive and remove before I sell to put on the next bike. Yes weird proportions don't help, but I now know what to look and feel for. If a bike's slightly too short, rather than put a longer stem on and push my weight forward - it's already generally a bit too far forward anyway as my torso is long for height - so I have to push seat back or put a longer layback seat post on. If I don't do this I'm cramped and get bad lower back and if not balanced I have too much weight on wrists. I probably need a stronger core, but what works for me is to test my balance whilst riding along. I put my feet at 3 and 9 O'Clock, hands on hoods and then slowly lift hands off hoods, if balanced I don't fall forward too much. If I fall forward, I push my seat back more to balance weight towards rear. If a bike is too short for my torso I end up not being able to push the seat back enough to balance me properly.

munkster

OK so I have got a SRAM 350 non-series PF30 chainset then. It came with a PF30 BB (it has sleeves, that differentiates it from BB30 am I right?) so my next question is: do I/can I just slot my PF30 chainset into a BB30 bottom bracket or do I have to remove the BB30 bottom bracket and fit the PF30 one? I'm well versed with HT2 bottom brackets etc but these press-fit things are a bit of a mystery with their circlip wotsits and what have you.

Any help appreciated ;-)

simonj

Both BB30 and PF30 have same internal diameter and width, the difference is the diameter of the outside bit of the BB that touches the frame. As such you don't get PF30 cranks, it's just BB30 cranks and you fit a BB30 or PF30 BB depending on what your frame needs. So yes it should just slide straight in. PF30 BB is for a PF30 frame and BB30 BB is for a BB30 frame.