# Going to 120mm travel on a Specialized Chisel (meant for 100mm)



## AlexValex (Oct 27, 2017)

L.E. I've found this post after writting mine: 120mm fork on a frame built for 100mm travel?
I see that it'll transform the 68 to 67 degrees headangle.

Probably this kind of question might have been repeated ad nauseam, but I couldn't find the proper answer.

I'm 40+, riding XC hardails, but not racing (anylonger)... and I've grown reluctant about carbon.
I want to build a dream bike around a Specialized Chisel alloy frame. But I want an 120 mm travel fork, instead of 100 (I'm having in mind Rockshox Sid 120mm, no remote lockout, 44mm rake).
Now, the Chisel alloy frame (68 degrees headangle) is recommended to work with 80mm travel in XS and 100 in S, M, L and XL. I'll have an XL frame.
Allegedly, the frame isn't tested for 120mm (whatever that means, for Specialized). But:
1. I guess the jump from 100 to 80 in XS size would grant a corresponding jump from L to XL.
2. Downcountry bikes like those of Orbea, Specialized and Merida, with the same geometry as their XC conterpart, but 120 travel instead of 100 would also suggest that the headtube doesn't need particular reinforcement....
3. the 68 degree head-angle is going towards trail geometry anyway.
So, my questions:
a. are there some serious counterarguments against such an increase in travel?
b. will the geometry be affected? (interested mainly in the headangle, it's clear that the bike is going to be a bit longer, and a bit taller - anyway, I'm going to employ only a two mm. spacer between headset and stem). If yes, how?
c. any other thing to have in mind?

P.S. This bike is intended for rather long, not very harsh, nor very fast tours, with some occasional bumpy downhills. Definitely no jumps: I like my wheels on the ground. But I'm 1.90m and 90Kg, not as fit as I used to... some vertebrae issuing warning signals and a shoulder dislocated a while ago... At the same time, I don't want to go full suspension. And I miss the plushness that I had on an 120 mm travel Manitou operating on a 27.5 bike that I used to ride 10 years ago.


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## SSsteel4life (Jul 1, 2016)

I have my new model chisel set up with 120mm, for around 7 months. It rips! The rear is real compliant for an alloy hardtail. Actually the harder I push it the more compliant it feels. Front wise, I want to try a higher TPI tire to soften it up a bit more to make it more in-line with the rear end compliance. Thou I only way 70kg, so may be even more compliant feeling for you. Currently running 60 TPI DC Maxxis rekon 2.4. This bike would be perfect for what you are doing and would rip if you want it to. I just got done doing a 2.5 hour ride pushing the bike hard on Blue trails with some moderately hard sections and lots of roots on the whole trail system. One downhill section was completely blown out from erosion creating good size step down like drops over roots and I could not believe how good the bike handled it being a hardtail.

I went with a Manitou Machete, had similar concerns, but since there AC measurement is lower than a comparable rockshox fork they place on them. AC wise it would be like putting a 110mm rockshox fork on. Therefore once in sag, really not a big difference between it and the 100mm rockshox they spec. Geometry feels on point, not much wondering on climbing, probably due to the lower offset fork. Bike just feels really balanced.


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## AlexValex (Oct 27, 2017)

SSsteel4life said:


> I have my new model chisel set up with 120mm, for around 7 months. It rips! The rear is real compliant for an alloy hardtail. Actually the harder I push it the more compliant it feels. Front wise, I want to try a higher TPI tire to soften it up a bit more to make it more in-line with the rear end compliance. Thou I only way 70kg, so may be even more compliant feeling for you. Currently running 60 TPI DC Maxxis rekon 2.4. This bike would be perfect for what you are doing and would rip if you want it to. I just got done doing a 2.5 hour ride pushing the bike hard on Blue trails with some moderately hard sections and lots of roots on the whole trail system. One downhill section was completely blown out from erosion creating good size step down like drops over roots and I could not believe how good the bike handled it being a hardtail.
> 
> I went with a Manitou Machete, had similar concerns, but since there AC measurement is lower than a comparable rockshox fork they place on them. AC wise it would be like putting a 110mm rockshox fork on. Therefore once in sag, really not a big difference between it and the 100mm rockshox they spec. Geometry feels on point, not much wondering on climbing, probably due to the lower offset fork. Bike just feels really balanced.


wow, thanks for these impressions!
Really encouraging! What size is your frame?
Also, glad to hear that it takes 2.4 tires (I'm running 2.25 on my alloy Scott Scale now).
I'm also considering the eventuality of "correcting" the slackering of the head-angle with the WoolfTooth Geo-Shift, adjustable headset, if case may be.


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## SSsteel4life (Jul 1, 2016)

AlexValex said:


> Really encouraging! What size is your frame?


I have a medium. Even with the 120 fork, I run 24mm spacer under stem, and run 15mm Riser bar. If you need stack perspective. I ride more upright. Fork un-sagged my bars are about 15mm higher then my seat. All my body dimensions are proportional. Looks like your Xl would have 28mm higher stack.


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## Jeremy05 (Oct 31, 2020)

I’m going to be swapping my fork out this weekend on my 2021 chisel. I currently have a 100mm Reba and will be installing a 120 Reba. The 100mm Reba is a nice stiff fork, but not all that plush. I decided to move to 120mm to get a slightly more plush feel and to slacken the bike out a little and make it less twitchy. I don’t race my bike at all and just do general trail riding. I’ll hopefully have an update next week on how the upgrade goes.


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## AlexValex (Oct 27, 2017)

Interesting that you want to slacken it a little more. I thought, on the contrary, that since the 120 fork will slacken the bike with 0.5 maybe even 1 degree, I'd use the Geo Shift headset to correct it, avoiding thus lifting the front wheel on steep climbs. I don't mind getting it to 68.5 degrees.
Fingers crossed for the update


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## Jeremy05 (Oct 31, 2020)

I calculated about a 1deg change with the 120mm fork, so it would go from 68 to 67 deg without any sag taken into account. I am hoping it won’t hurt to much on climbs, but that is one of my concerns. There’s not a lot of threads out there on 2021 chisels with 120mm forks, but the few I have read everyone seems to like the extra stability of the slacked head angle. I don’t race this bike, but my trails do have a lot of roots. Extra travel and slacken head angle will hopefully make me more stable at speed. I love the chisel for how light and fast is, but in hindsight I probably should have bought a Fuse for general trail riding.


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## DeoreDX (Jul 28, 2007)

Even if you could feel the nearly imperceptible difference raising the front end 20mm after the first ride your brain and body will adapt and it will feel "normal". If a 20mm longer forks and 3/4 of a degree change in angle raises the stress in the head tube/down tube junction enough to cause a failure it was woefully under designed and destined to failure in the first place.


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## Jeremy05 (Oct 31, 2020)

I did some looking into the 120mm Reba and it looks like the axle to crown is about 5mm longer than the Manitou Machete. Do you think that will make much of a difference in handeling when switching to a 120mm? Also, the Reba is a 42mm offset vs the 51mm. Just wanted to get some feedback before I install the new fork.


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## Arm&Hammer (Dec 19, 2020)

You will not have any issue with climbs at 67 degree. Maybe have to get used to it for a few rides. I have a HT with a 64 degree and have no issues on steep climbs.


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## Jeremy05 (Oct 31, 2020)

So I changed the fork on my 2021 Chisel and went out for a trail ride. I could tell a big difference in the way that the bike handles now. It was a lot more stable on the down hill section and I felt a lot more comfortable riding the downhills fast. The ride was also a lot softer with the longer fork. I was able to stay in the saddle through sections that would usually get very rough. I really did not notice any problems with climbing, if any thing I think that my front wheel did a better job keeping planted to the ground than it did with the Reba 100. The one thing that I noticed that I did not like was in the slow section I could feel more wheel flop than before. I'm sure that is due to the head angle change. It was not terrible, but it was slightly noticeable. All in all I really like the way that the chisel handles with this fork. 

I am wonder if I reduced the fork to 110mm if it would reduce the wheel flop, but keep most of the stability. I'm still researching if it is possible to change the fork to 110mm. According to Rockshox's website the fork is offer as a 110mm, but I can not find anywhere that sells it. And the only 110mm airshafts i can find are for the Reba A3 and don't say if they will work on the Reba A8. More than likely I'll keep it the way that it is because it was a lot of fun.


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