Fork Upgrade

[mikebn]

I have a Trek 3700 with a RST 191 fork with a reported travel of 63mm. I want to upgrade to something that will take some bigger hits and more travel. I’m looking at the Rock Shox Tora 302 or 318 as a possible upgrade. My bike has a 70degree head tube, and the Tora’s have a travel range of 85-130mm. Is this a good upgrade or is the extra travel a bit too much? I figured, on the low end, it is about an inch more travel than I have now. Which should still be good for climbing, and still not too much nose up attitude. What does all the techies out there think?

I’m also upgrading the entire drive train at the same time.

thanks in advance for your input.

[Bombardier]

You won’t have any problems fitting a RS Tora on your Trek; steering or otherwise. It’ll slacken your head-tube angle a degree or so; if even that much, once you figure in sag. With that RST fork your Trek already has, you’ll be lucky to actually get 63mm of travel…. 40-50mm of pogo-stick bounce is more like it.

But instead of spending the coin to upgrade your fork and drivetrain on a Trek 3700, you would get more for your hard-earned dollars (or tax rebate check 😀) if you just bought a bike with higher-end components already hung on it. Buying aftermarket parts seperately is much more expensive.

[AK_Dan]

Ive been having issues with the 302, had one go bad after a year, went down and only came back up half way. not having the time to wait for parts I bought another one. $300 later and two states away it starts leaking out of the dampening adjustment and now the top where the lock out is. Rock Shox says they will be happy fix it under warranty but I need to remain in one place long enough to have them send parts to a bike shop- that aint happening cause im in the middle of a road trip so some of this is my fault- just a bit peeved I guess.
I weight almost 190, if you weigh that much or are any heavier I would get a heavier duty shock to begin with, these dont seem to hold up.

[cjm]

Before you upgrade your fork it is important that you contact your frame manufacturer (Trek) and find out if the crown-to-axle of the new fork exceeds the maximum limit for the frame. Mostly what you will do is void the warranty on your frame. But, it’s not unheard of that you will break your frame. This is what Kona sent me what I asked about putting a 160mm fork on their "Bass":

"Putting a longer fork on will unbalance the handing, put extra bending vs. compression force into the fork since it’s no longer held at an optimal angle, and most likely damage the frame in a big impact."

A big impact is relative to the bike. What is normal impact to my Norco Shore might be a big impact to your 3700. Trek would know for sure.

When you slack your HTA (head tube angle) you will be allowed to, and might even have to, carry more speed through rougher sections. On a hard tail, more so than a full squish, this is going to put more stress into your cranks from increased lateral forces. Further, the beating on your rear wheel will shoot up as well especially, if you’re not getting full travel from your knees. A beefier fork might also require a beefier headset.

Rather it’s a high-end 4X bike or entry level hardtail, bike companies have a certain type of riding in mind when they build frame and spec a bike. The easiest way to over-stress a design is to over-slack the HTA by putting to much fork on the bike.

This a lot of text to agree with bombardier, your money would be better spent on a new beefier bike. It’s not much of stretch to see a $250 fork upgrade costing you $500+ before the mid-point of the season. Add downtime to wait for repairs and suddenly the $1000 for a shiny new Trek 6000 series doesn’t seem as bad. Especially with Trek offering interest free loans.

[mikebn]

Thanks for all the advice. I did hear that the 2007 302 did have blowby problems. But that was cured in the 2008.

Ill have to check if Trek says it will over stress the frame. I have mixed stories there. My big concern was the extra travel and climbing. I don’t want to be too nose up. Thats why the adjustable travel sounded good. Does anyone know of a good fork with less travel?

As far as the new bike. I’m still in wish mode. This was to milk my current bike out until I am able to save up for a new one. I’m looking at the new 2008 Trek Fuel. I figured a couple inexpensive upgrades would suffice for now. Maybe I need to rethink. hmmmmmm

[mikebn]

Thanks for everyones help.

I ended up talking to Trek and there was no problem with a fork upgrade. I found a Marzocchi XC 700 on sale and went for it. 100mm travel with their ETA travel adjust for climbing. A lock out and rebound adjust with Air preload. Not a bad deal. All with an upgraded drive train (chain, Cranks/rings, freewheel/cassette).

This bike is awesome. A few more adjustments/tweaks and Ill have it dialed in.

Check out My bike pics for a finished product.[/img]

[cjm]

Zoke’s seals and springs can take a while to break in. After they broken the ETA is awesome. ETA is Zoke’s best travel adjustment.

[mikebn]

"cjm" wrote

Zoke’s seals and springs can take a while to break in. After they broken the ETA is awesome. ETA is Zoke’s best travel adjustment.

Thanks for the info CJM. They did say to give the fork a couple of rides to get it all working together. It seems a little stiff right now, but I’m hoping it will loosen up. The ETA is pretty sweet. It works great. I switch it in just before a good climb and bounce on it to set the travel, and away I go. I feel like its the best investment I could do for the price, (and the price of the bike).

[spazjensen]

I have the same Marzocchi fork and have been riding on it for the past four months. I put through some nasty hits and landings and it hasen’t failed me yet, and certainly hasen’t given any in dampening or rebound. It sure has done me well. I weigh in a hefty 250 and it well; it has never bottomed out as far as I could ever tell with all the stuff I put it through.

[mikebn]

Thanks spazjensen.

have you been able to adjust the Air Preload on your fork? I found a cap on the bottom of the left leg, but I can’t get it loose. Have you seen the connector to add/remove air pressure?

I was also told that under the red lever on the top right leg of the fork hides another air adjust connector for the Pos rebound. Can you verify there is an adjustment there to? Both caps are nearly impossible for me to remove(on too tight). Let me know if you had similar experiences.

[spazjensen]

Honestly I have not had the situation with not being able take the bottom caps loose. The adjustment lever that you mentioned should be the correct one for the rebound. I have only had mine added once and I took mine to the shop. Never thought about asking the guy how he did it.

Sorry, not much help is it?

[mikebn]

Thanks anyway. I think I need to take it in and have someone check it out.

[spazjensen]

Yeah. That’s usually what I like to do when I am not sure about how to make adjustments in new equipment that I am not familiar with. Just remember to ask the shop guy about what he did and basically how to do it yourself. He shouldn’t mind to much if he’s a nice guy.

[mikebn]

i took it in and they found two air ports under the ETA and ATA caps on the top of the fork legs. I adjusted the pressure according to Marzocchi and It rides really nice now. The shop doesn’t buy the idea of an air port on the bottom of the left leg for Preload though. They feel the cap there is actually the fixture to hold the fork together. Oh well. It works great now. Ill leave well enough alone.

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