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ibleedblackandgold said:
Hi guys, I am looking at a Marzzo Marathon S that has a real good price,but the travel is 120mm. Can my frame's geometry comfortably handle this beast? Any thoughts will be appreciated. Thanks
If your running an 100mm right now then it will make a difference and if your running an 80mm it will make a big difference in the way the bike handles (ie Steering). A big change like from 80mm to 120mm could almost reach a point where you bike can be unsafe due to added stress being put on the frame (ie steer tube) On the other hand if your doing big drops then it may be desired to stretch out to 120mm of travel. If the Marathon S has an adjustment that allows you to set the amount of sag in the fork then you could increase the amount of sag and thus reduce the ride height slightly. Just a thought. I think I would go that far, but thats just me. :D
 

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I wouldn't put the fork on. The 4300 came with an 80mm fork, right? A 120mm fork will definitely change the head angle (by about 4 degrees). Also, you'll probably be putting more stress on the head tube than it was originally designed for. If you put that fork on, chances are you'll void your warranty.

Here's what I would do if I were you: You've probably put in enough trail time by now to decide if you really want to stick with riding MTB's. If you're really into it, just ride the 4300 until it can't go anymore, then buy a new bike with the components you want. Or sell it and use that money for a new bike. I really think that you would be throwing your money away if you upgraded the fork on the 4300. The only upgrade I would consider for an entry level MTB is a set of good pedals.
 

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bi-winning
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ibleedblackandgold said:
my head angle is 70.5. If I increase my suspension by 40 mm, wouldn't that give me an angle of 72.5 which is optimum?
I think it is the other way around. a longer fork will give a slacker angle rather than steeper. you will probably bring it into the 60's.

Most people strongly object this much of a change. Too much stress on frame, poor steering and climbing.
 

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Domestic Fowl
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Below is my reply to a similar question in this forum. I'm less concerned about stress on the frame than I am about the change in ride and fit characteristics. Putting a 120mm fork on a bike designed for 80mm fork will change more than just the head tube angle.

See below.

FreeRangeChicken said:
You need to be really careful or you're going to end up with a really expensive wall ornament.

If your current bike has a 50mm fork and was designed for that fork, you could run into some big problems if you just slap a long travel fork on it. A few things are going to happen when you stick a longer fork on your bike:

1) loss of standover height - if you have a lot of standover right now this may not be a big issue, but if you only have an inch or two now, it cold be a problem

2) slackening head tube angle - This will slow down steering and if the change is dramatic, can cause the steering to feel like it flops from side to side. [edit]this also tends to unweight the front tire which can cause the front tire to wash out in corners[/edit]

3) slackening the seat tube - this shifts your weight backwards and may make it difficult or impossible to climb without lifting your front wheel off the ground.

I had a bike that I changed from a 64mm fork to a 80mm fork and found the setup to be completely unacceptable for me. You're talking about going from 50mm to 75-100mm. That's huge. If at all possible try a longer fork on your bike before you buy something.

I'm not trying to discourage or dissuade you. Just trying to make you aware of the possible pitfalls.

Good luck.

FRC
 

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suck it trebeK
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I have a Trek4100 and went from its crap 63mm fork to an 80mm Air fork. No problems at all. Have to lean a little lower only on the steepest of climbs, but it's welcome on the downhills and increased travel. That and not being a boat anchor that the stock fork was.

Got a deal off eBay so I didnt spend much. Only bout $90US.
 

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trek

i have around a year 01 trek 4500 and i believe it's crappy rockshox jett has like 65mm of travel? i could be wrong but i know it's nowhere near 80mm. i would stick with an 80mm or 100 max if it's got an 80 on it now. for that frame, like the above posts, too much and you're trying to turn the bike into something it's not... i've done exactly what you're thinking -
i put a 125mm psylo on my xc bike that had a 80mm judy and i was killing it - it's xc characteristics were gone, it was creaking... i put her back to the 80mm and all was good.
 

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Discussion Starter · #9 ·
THANKS to everyones comments. I contacted Trek today, and they agreed with you guys that 100mm is the max for travel on this frame. They said since Marzo 105 forks crown length was about the same as Rock Shox 100, that would work too. So, I just ordered a 04' MX Comp Air 85mm from Pricepoint. I am still learning obviously, and thanks to you guys and to Trek, I didnt have to learn the hardway this time.
 

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otbmbc.com
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ibleedblackandgold said:
THANKS to everyones comments. I contacted Trek today, and they agreed with you guys that 100mm is the max for travel on this frame. They said since Marzo 105 forks crown length was about the same as Rock Shox 100, that would work too. So, I just ordered a 04' MX Comp Air 85mm from Pricepoint. I am still learning obviously, and thanks to you guys and to Trek, I didnt have to learn the hardway this time.
I have an '05 Trek 4300 and I put a Marz 105 EXR Pro on it. It rides great. It feels great and solid. The bike's slope does appear steeper but I don't feel any negative ride characteristics. I actually feel safer decending. I put a RaceFace stem with a lower angle on it and now it climbs better than before.
 

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i have 120mm on my 4600

I have a Trek 4600 and i have a 120 mm travel Marxocchi mx pro eta. I believe all the 4 thousand trek models are the same frame right? mine is a 19.5" frame would different frame sizes have different head tube angles? I love the extra travel, gives me so much more confidence. Plus, i can lock it out for the long climbs. The bike feels better with the extra travel in my opinion.
 

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Is it that important for you to upgrade the travel of the fork? If not just stik with the 80mm fork, but yet upgrade to a beefier fork different brand taht is stronger, but same travell. There it will be able to take the beating, and ur ride head will have staed the same.
 
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