SRM cranks Q factor: Pro cranks vs Dura Ace SRM

[BdaGhisallo]

Anyone know what the Q factor is for the SRM pro cranks and how it might differ from the H-Tech Dura Ace cranks they modify with their spider?

I am thinking of getting a second powermeter and the regular pro pm is cheaper than getting a second DA pm. However, if the Q factor is that different it might throw a fly in the ointment.

Any ideas?



And, to be sure, when I say Q I am referring to the distance between the crank arm faces where the pedals thread in. The width of your feet's stance when pedalling.

Thanks.
Geoff

[cambo]

I'd love to know this too. I wrote to srm last week for anwser but no reply yet. I've searched there site and nothing either. i want to use srm pro in training but dura ace cranks on big races, but if the q factor is too different it might feel funny on race day

we just need someone too measure it themselves by putting both cranks facing foward and using some measuring calipers, digital would be best

[zakeen]

The SRM DA has the same Q-factor as a normal DA crank.

The SRM PRO(non DA,FSA.....or whatever) has a Q-factor of whatever you want. You can change this by using different BB sizes. 105,107,109,111,115 etc........

[cambo]

The SRM PRO(non DA,FSA.....or whatever) has a Q-factor of whatever you want. You can change this by using different BB sizes. 105,107,109,111,115 etc........

But I thought that the octalink bb only came in either double or triple chainring lengths??

[Taz]

The SRM DA has the same Q-factor as a normal DA crank.

The SRM PRO(non DA,FSA.....or whatever) has a Q-factor of whatever you want. You can change this by using different BB sizes. 105,107,109,111,115 etc........

Agreed but this will also affect the chain line.

[zakeen]

But I thought that the octalink bb only came in either double or triple chainring lengths??

This Im not sure, you might be right as I was talking about the Square Taper version. I wouldnt get the Octalink as this is "tech" thats dieing!

Square taper will be around for ever. There are many options for stiffness versions and light ones. Also different sizes.

[zakeen]

The SRM DA has the same Q-factor as a normal DA crank.

The SRM PRO(non DA,FSA.....or whatever) has a Q-factor of whatever you want. You can change this by using different BB sizes. 105,107,109,111,115 etc........

Agreed but this will also affect the chain line.

Yes chain line will be affected when you change the BB length. However BdaGhisallo was asking about Q-factor.

I played around with Q-factor a while ago with my SRM and never had any problems setting up the gears with different Q-factors.

[Taz]

The SRM DA has the same Q-factor as a normal DA crank.

The SRM PRO(non DA,FSA.....or whatever) has a Q-factor of whatever you want. You can change this by using different BB sizes. 105,107,109,111,115 etc........

Agreed but this will also affect the chain line.

Yes chain line will be affected when you change the BB length. However BdaGhisallo was asking about Q-factor.

I played around with Q-factor a while ago with my SRM and never had any problems setting up the gears with different Q-factors.

So we both agree

[BdaGhisallo]

Thanks for the help guys.

[yourdaguy]

Most Q's are fairly close (around 147 with average BB), but one thing you can do depending on pedal/cleat/shoe type is that there is often a small amount of adjustability in the placement of the cleat that could compensate for any differences.

[zakeen]

So we both agree

Yeap. I just wanted to clear up the Q-factor part.

[django]

zakeen,

Thanks for the information! I've been wondering about the Q factor on the SRM Dura ace cranks.

[wilmar13]

i want to use srm pro in training but dura ace cranks on big races...

Perhaps slightly off topic, but as someone who is almost ready to pull the trigger and order a D/A SRM to use on two different bikes (for training, racing and TT... all uses), I am curious why you would want to race and train on different cranks? Is there an advantage to doing so, or a disadvantage to not?

[cambo]

i want to use srm pro in training but dura ace cranks on big races...

Perhaps slightly off topic, but as someone who is almost ready to pull the trigger and order a D/A SRM to use on two different bikes (for training, racing and TT... all uses), I am curious why you would want to race and train on different cranks? Is there an advantage to doing so, or a disadvantage to not?

I'd train on D/A Srm but can't afford it so have to settle for the pro model. big races don't need the powermeter so will go with the lighter and stiffer dura ace cranks.

i think it is only recently that we are seeing people "racing" on powermeters. they used to be training only. but since the dura ace and fsa models became available and the 6.8kg rule came in it's easier to have light bike with powermeter.