Strike One!

[2manyoranges]

I found a while ago that I was getting a lot of pedal strikes on my Ragley mmmBop - about two or three gapooows per ride on rooty singletrack - even though it had a long travel fork (150mm) it’s got a brutally low bottom bracket. The pedal strikes seemed to be more than just the result of poor technique since I was not having the same issue on my other hard tails. I was running 170 cranks and in line with the latest ‘go short’ drive, I put in some 165 XT cranks, thinking that 5mm change to the ground clearance would make no difference whatsoever. It sure made the gearing feel different, and it took a while to get used to going into a lower gear and spinning up. But the surprise was that pedal strikes promptly stopped almost completely. It’s possible that in doing the change I was just becoming more conscious of pedal position but I don’t think it was that. Only 5mm difference in the crank seemed to eradicate pedal strikes - very surprising and interesting….

 

[fishyfool]

Out of curiosity, were they 175 cranks that were drilled and threaded at 170? Your change to the XT cranks would have felt like 5mm but it would have ended up giving you 10mm if that were the case.

 

[2manyoranges]

Good question - but they were XT 170s, forged and drilled for 170. I replaced them with some nice 165 XTs I managed to pick up….

 

[clubby]

Out of curiosity, were they 175 cranks that were drilled and threaded at 170? Your change to the XT cranks would have felt like 5mm but it would have ended up giving you 10mm if that were the case.

They only tend to do that on cheaper cranks.
Because Shimano Holowtech are, well hollow, you can’t do that with them anyway.
Had that issue (look away now 2manyoranges) on my ebike. Whyte pushed the boundaries of low on their first gen and I’m now running a 155mm (from 165) which has solved it. Telling that they increased bb height on later models.
Even pedal size can make a difference. I swap between flats and spd on the same bikes and catch more pedals on flats even though the body is thinner. Just shows some of the margins of it happening.
For me, bb height is as low as it can or indeed needs to go, I cam even see it going back up slightly.

 

[2manyoranges]

They only tend to do that on cheaper cranks.
Because Shimano Holowtech are, well hollow, you can’t do that with them anyway.
Had that issue (look away now 2manyoranges) on my ebike. Whyte pushed the boundaries of low on their first gen and I’m now running a 155mm (from 165) which has solved it. Telling that they increased bb height on later models.
Even pedal size can make a difference. I swap between flats and spd on the same bikes and catch more pedals on flats even though the body is thinner. Just shows some of the margins of it happening.
For me, bb height is as low as it can or indeed needs to go, I cam even see it going back up slightly.

Clubby - That’s really interesting … in terms of human performance I think we build a very complex mental model of the relation between all parts of our body and the outside world and am sure that you are right, it leads to very tight margins over roots, lips, rocks etc of which we are just not aware. I know that I miss trees with the ends of my bars with tiny tiny margins…it’s phenomenal what the less conscious mind can do, and that’s why looking we’ll Clubby - That’s really interesting … in terms of human performance I think we build a very complex mental model of the relation between all parts of our body and the outside world and am sure that you are right, when we let the less conscious mind do things (eg by looking well forward) it’s just amazing how we do things with tiny margins - I know my handlebar ends miss tress by tiny tiny margins…

 

[2manyoranges]

They only tend to do that on cheaper cranks.
Because Shimano Holowtech are, well hollow, you can’t do that with them anyway.
Had that issue (look away now 2manyoranges) on my ebike. Whyte pushed the boundaries of low on their first gen and I’m now running a 155mm (from 165) which has solved it. Telling that they increased bb height on later models.
Even pedal size can make a difference. I swap between flats and spd on the same bikes and catch more pedals on flats even though the body is thinner. Just shows some of the margins of it happening.
For me, bb height is as low as it can or indeed needs to go, I cam even see it going back up slightly.

Clubby - That’s really interesting … in terms of human performance I think we build a very complex mental model of the relation between all parts of our body and the outside world and am sure that you are right, when we let the less conscious mind do things (eg by looking well forward) it’s just amazing how we do things with tiny margins - I know my handlebar ends miss trees by tiny tiny margins…