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Freeride MTB front end, stiff enough for a fiddy?

JohnRobHolmes

JohnRobHolmes

owner, Holmes Hobbies LLC
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Here is a front end I just completed. I don't know if it will be rigid enough for a road use CRF50 motor'd rig. What do you guys think? Top speed will probably be around 45mph

'03 Marzocchi Super Pro
custom wheel
shinko 244 DOT tire
Hayes stroker 8" rotor brakes?

For the wheel I laced a 17" motorcycle rim into a Marzocchi 20mm front hub with 10ga stainless motorcycle spokes. I did have to drill both the hub for spoke clearance, and rim for the nipples. For the rim strip I used a MR Tuffy liner for bike use. Perfect! Pumped it up to 33psi and it rides very solid on my street bike (bicycle).


My concern is that the fork will be a bit flexy under hard breaking. Total vehicle weight will probably be 150, and I weigh 150lbs. The stanchions are 32mm from top to bottom.
 

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it will flex , how much im not sure , i used to ride freeride/down hill and i had a jrt laying around that i threw on my bike just to ride. (JrT is ther exact same as the supert minus the compression and rebound adjustments) and it flexd way to much for my likeing especially under brake and turning, you can definatly see/ feel the whole fork twisting. the bike was 65lbs and im 190. i went on about 2 rides befor i just stuck the bike away and waited for my other forks to show up and was much happier when they did.. IMO try and track down a Monster t fork, they are biiger, stonger stiffer and heavier but damn near bomb proof, the stanctions are in the 40mm range i beleive the 02 and older are 7" travel with the 20mm axle right on the bottom (like that super) and the 03 and newer are 8" but with the axle mount a few inches up the lowers, so ride hight will be about the same as that fork
 
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One of my good friends has a super T fork on his DH bike and it flexes too much for my preference. It is very noticable under hard braking and even in berms. I weigh 190 and the bike was ~50 lbs.


I had a '01 monster T for a while and it was VERY stiff but I sold it because it wasn't as adjustable as I like. I now run a White Bro's DH2 and it's by far the best DH fork I've ever ridden.

Edit: Kenny, I believe the stanchions are 32 mm
http://www.marzocchi.com/Template/detailSPAForksMTB.asp?IDFolder=113&LN=UK&Sito=mtb&IDOggetto=2447
 
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I would look more at the steerer tube & fork clamps being weak & bending or the tube pulling out of the fork clamps. the tubes would be fine but you would get some deflection out of them
 
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Lower legs are about 1.5" diameter. Stanchoins are 32mm.


Looks like this one will stay on a light electric motorcycle or bike only. Just seems too flexy for a heavy bike going fast. Maybe I will put it on the LeToy.
 
Hmm are mtb forks like mx bikes? Could you tear them apart and rebuild them stiffer with springs, valving, etc? Seem's logical...
 
Yeah, these are rebuildable with external compression and rebound adjust. I have stiff springs and could get some heavier oil for them. I am worried about the forks flexing though, not so much the compression or rebound.
 
What is the intended purpose? If its a street E-bike, no problem, if you will be jumping it (or let Jeff ride it) you need more fork.
 
Street bike with 50cc honda motor, about 40lbs worth dry. I may end up jumping it a little, after how I rode my E-bike last night.
 
Get a set of BBR forks.Careful of the price :shock:
I'd try what you have,especialy at your light weight.If it flexes too much for your riding style try somthing else.
 
Yea, the load is placed more on the bearings & headtube, also the fork clamps are a lot beefer that on the MTB forks so the load is spread out a little more to other places.
 
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