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Crank Rock Strikes

Jan. 24, 2021, 4:09 p.m.
Posts: 12
Joined: March 11, 2012

Looking for people's experiences with rock strikes on cranks. Just entered the modern era with a new to me/used 2019 Rocky Instinct BC Edition, coming from a 2011 Titus Rockstar. Running the same length cranks (170mm) on both bikes but I sure seem to graze/get uncomfortably close to more rocks at the bottom of the pedal stroke than ever before. What am I missing here? By no means am I up to speed on any of the effects of new geo and frame design. One thing I can say is "whoa! magic carpet ride". Thanks for any input. Cheers, Ray

Jan. 24, 2021, 4:41 p.m.
Posts: 316
Joined: Feb. 24, 2017

Modern bikes are very low. My bike came with 170mm cranks. While I was waiting for my 165mm to arrive I rode about 100km on the 170mm. I would hit the most random things. Now that I have 165mm cranks I only hit if I am not paying attention. I also no longer run carbon cranks.

Jan. 24, 2021, 5:37 p.m.
Posts: 794
Joined: March 15, 2013

I hit my cranks like 10 times on a ride. 

In fact the last ride I went on I hit my left crank and foot so hard i broke my shoe :/

Jan. 24, 2021, 5:43 p.m.
Posts: 817
Joined: May 11, 2018

When I switched from a hardtal to full sus, I was hitting things all over the place. After a few months, without changing anything, I had almost no rock strikes. You just have to get used to it.

As for a power meter, personally I'd go for something aluminum. In the last five years I have only had issues with carbon cranks. My old turbines just go and go. If I were to invest in something like a crank arm power meter aluminum is the easy choice. Maybe Shimano?

Jan. 24, 2021, 7:21 p.m.
Posts: 646
Joined: Jan. 31, 2005

I have a super low BB 6" 29er and 175mm cranks and I almost never have pedal or crank strikes. Maybe I did more at the beginning and have just learned to time my pedal strokes carefully.

Jan. 24, 2021, 7:49 p.m.
Posts: 1780
Joined: Feb. 26, 2015

Posted by: craw

I have a super low BB 6" 29er and 175mm cranks and I almost never have pedal or crank strikes. Maybe I did more at the beginning and have just learned to time my pedal strokes carefully.

My bike has a super low BB. Learning to do ratchet strokes really helps avoiding the strikes.

Jan. 25, 2021, 6:13 a.m.
Posts: 567
Joined: Sept. 10, 2012

After having a low BB "modern" bike and getting far more pedal strikes than I enjoyed [...yes I can ratchet...no I don't want to think about my feet/pedals all ride...] I was on the look out for a new FS bike with a higher BB. I noticed the GG Smash was such a bike. It's so nice being able to pedal through our rocky/rooty trails without hitting my pedals. Having ridden the same trails on low and high bikes I don't notice any major performance difference other than the lack of pedal strikes. That said I am allergic to flow trails and berms so my experience could be due to the nature of the natural trails I like to ride.

You can make a significant difference in pedal strikes by choosing shorter cranks and thinner/smaller platform pedals. If your trail has few obstacles you can ratchet through them. You can get silicone crank boots to protect the ends of your cranks to some degree.

I just keep BBH in mind when looking at new bikes. If the BB is too low I move on.


 Last edited by: Vikb on Jan. 25, 2021, 7:18 a.m., edited 1 time in total.
Jan. 25, 2021, 8:15 a.m.
Posts: 646
Joined: Jan. 31, 2005

Posted by: Vikb

After having a low BB "modern" bike and getting far more pedal strikes than I enjoyed [...yes I can ratchet...no I don't want to think about my feet/pedals all ride...] I was on the look out for a new FS bike with a higher BB. I noticed the GG Smash was such a bike. It's so nice being able to pedal through our rocky/rooty trails without hitting my pedals. Having ridden the same trails on low and high bikes I don't notice any major performance difference other than the lack of pedal strikes. That said I am allergic to flow trails and berms so my experience could be due to the nature of the natural trails I like to ride.

You can make a significant difference in pedal strikes by choosing shorter cranks and thinner/smaller platform pedals. If your trail has few obstacles you can ratchet through them. You can get silicone crank boots to protect the ends of your cranks to some degree.

I just keep BBH in mind when looking at new bikes. If the BB is too low I move on.

That totally makes sense. I love the way low BB bikes ride but it's definitely possible for the BB to be too low. I'm on a bike now with a workable compromise that doesn't make me feel like I'm concentrating on ratcheting the whole time. Gotta find a happy balance. It's great that we have lots of options in bike geo that people can find something to suit their preferences. This aspect of bike design has really come a long way.

Jan. 25, 2021, 9:53 a.m.
Posts: 2927
Joined: May 23, 2006

Posted by: Vikb

I just keep BBH in mind when looking at new bikes. If the BB is too low I move on.

I won't even consider anything lower than 340mm for full sus.

Anyone want to buy a used Transition frame?

Jan. 25, 2021, 9:56 a.m.
Posts: 2384
Joined: Sept. 5, 2012

All part of the sport 'IF' you ride no groomed trails. I run alloy cranks as well. Boots do help on carbon cranks. But they still can have the pedal thread get trashed. At least with alloys they are typically half the price to replace.

Jan. 25, 2021, 9:58 a.m.
Posts: 2384
Joined: Sept. 5, 2012

Posted by: Vikb

After having a low BB "modern" bike and getting far more pedal strikes than I enjoyed [...yes I can ratchet...no I don't want to think about my feet/pedals all ride...] I was on the look out for a new FS bike with a higher BB. I noticed the GG Smash was such a bike. It's so nice being able to pedal through our rocky/rooty trails without hitting my pedals. Having ridden the same trails on low and high bikes I don't notice any major performance difference other than the lack of pedal strikes. That said I am allergic to flow trails and berms so my experience could be due to the nature of the natural trails I like to ride.

You can make a significant difference in pedal strikes by choosing shorter cranks and thinner/smaller platform pedals. If your trail has few obstacles you can ratchet through them. You can get silicone crank boots to protect the ends of your cranks to some degree.

I just keep BBH in mind when looking at new bikes. If the BB is too low I move on.

Think the newer GT has a 349mm BB height. I remember people freaking it was too tall and would be unstable . Has not slow Martin Maes down at all LOL

Jan. 25, 2021, 10:35 a.m.
Posts: 12
Joined: March 11, 2012

Thanks everyone for all the great replies! As I thought the BB is a bit lower than my previous rigs. It was pointed out to me at time of purchase that it may be tough going to a new geo from my old school trained nervous system (if that makes sense). The comments that resonate with me is that it would be nice to not have to think as much as I have been, so far, on rides about trashing my cranks and associated bits. 

I also agree about going with shorter cranks such as 165s. Anyone run shorter than that? 

Once again thanks for the all the replies, a great affirmation of community here. Glad to be making the foray out onto the trails more again and rediscovering my roots (and rocks 😉).

Cheers!

Jan. 25, 2021, 11:33 a.m.
Posts: 118
Joined: March 1, 2017

My armchair engineering thinks that as wheelbases get longer, BB heights should actually go up a bit in order to get the same amount of effective clearance. We are already gaining shed loads of stability through wheelbase, head angles and chainstay length, that I'd sure BBs could go back up a few mm without having too much negative impact on either cornering or straight line stability. There are sections of trail that I just can't be arsed to ride these days due to having to get pedal positioning / ratcheting 100% perfect. On an old Bullit with 66s I've just ride through it without a care in the world! I don't think we need to go back to those days but there could be a bit more of a compromise.

Edit: I've just checked the BB height on my hardtail and it's only about 15mm higher than bikes I had in 1989, yet the fork compresses 160mm! I do love the way the bike rides, but with a 70+BB drop, I wonder if it'd ride any worse for adding 10mm to the BB height.


 Last edited by: trumpstinyhands on Jan. 25, 2021, 11:38 a.m., edited 1 time in total.
Jan. 25, 2021, 11:52 a.m.
Posts: 1130
Joined: May 4, 2006

Also consider the sag of your shock....

Anecdotally, I seem to have more rock strikes when I've lost a few PSI from my shock. I must remember to check my shock pressure more often. 😳

Jan. 25, 2021, 12:20 p.m.
Posts: 2
Joined: Sept. 1, 2010

I had a 2016 Instinct until recently and always felt I was getting a lot of rock strikes, especially when the Ride 9 was flipped into a low setting. I saw on your other post that you're running the Next SL's - I was always glad I had the boots on them.

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