Singlespeed & Fixed Gear - How much Rake?
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08-19-08, 12:57 AM
I am riding a Dawes SST wich has a 70 degree head tube... unfortunatly i cannot find anywere that lists the sweep on the fork... I would like a bit tighter ride, and have been looking into a set of forks as a fix, instead of rushing into a new frameset.
So, two real questions:
A) Does anone know the fork sweep on the stock dawes SST fork?
B) How much rake seems reasonable with a 70* head tube.
08-19-08, 01:23 AM
bike in question
With a headtube that slack, you cannot attempt to quicken the steering with a low rake fork without sacrificing stability. I would use one of those online fork rake calculators (google search, they all do the same math even if they are made for motorcycles instead of bicycles) to find what rake you need to achieve the desired trail distance for a 70* HT. Start by entering a typical road frame HT angle of 73* and 40mm rake, assuming this is the kind of handling you are trying to achieve. Then calculate the trail distance this gives. Now enter that trail distance and the 70* HT angle into the calculator and solve for the the new rake. I think the number you will get is really low...
EDIT: Oops, I guess you do want more rake (less trail)...I try not to get those confused...Here's a decent calculator for doing the math:
You want more rake, not less, if you want to make the handling "quicker".
The bikesdirect owner posts here often, I'd suggest changing the title of this thread so he recognizes it or PM'ing him.
08-19-08, 11:55 AM
The Dawes SST has a 72 degree heatube angle...not 70.
72 is not unusual. Cyclocross frames and small sized road frames typically have a similar head tube angle. Typical road bike geometry usually involves a head tube that is steeper by only 1-1.5 degrees. Thats not much.
Decreasing the rake will make your bike look tighter, but it will handle more sluggishly. I have no idea what the rake is on the stock SST fork, but for that frame I would want something around 45 mm, perhaps a little more, but not much more.
08-19-08, 12:04 PM
08-19-08, 12:12 PM
Just be careful the first time you bomb a long hill. Changing the rake may increase the risk of shimmy which could lead to a bad crash.
There was a long thread in the Roadie forum about this; guy gets new fork then experiences violent speed wobble while going downhill. Turns out the trail on the new fork was less than the old one(rake was more).
08-19-08, 01:13 PM
I've done some searching around back when I was looking into different forks for my 54cm Dawes SST, and while I can't remember my sources or how I figured it out, I think I remember the stock fork rake to be 43-44 . Again, I don't remember my sources and have nothing to back that up besides my memory. So pretty much this post is worthless and I'm just wasting time at work.
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