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-   -   Rigid Fork on 29er? (https://www.bikeforums.net/mountain-biking/1220522-rigid-fork-29er.html)

iamtim 12-30-20 03:30 PM

Rigid Fork on 29er?
 
So, since selling off all my road bike stuff (I was hit by a car and had a couple of other close calls; I don't want to ride in traffic any more) I've been toying with getting into MTBing on my local (very flat, very beginner friendly) trails. For Xmas, my GF got me a Cannondale Trail 7. I'm a tinkerer and can't leave a bike well enough alone, so I've already converted it to 1x9.

I really dislike the fork; if it had lockout it would be OK, but it doesn't. I'm seriously considering going with a rigid fork, since the riding I do wouldn't really need a full suspension fork.

So here are my questions:

1. Does the Trail 7 have a tapered head tube?
2. What are my options for a rigid fork? I've seen talk of "suspension corrected" forks, I'm not sure if that's actually a thing, or if any 29" fork that is close to the geometry will work.

Anyway, any feedback, tips, or pointers you all have would be great.

mack_turtle 12-30-20 04:08 PM

what year is the bike? got a photo? I can't offer any specifics until I see that.

if the head tube is 44mm, 34mm, or tapered in some way, there are plenty of options out there. you might need to replace the bottom half of the headset.

70sSanO 12-30-20 04:11 PM

Supposedly, it has a 100mm SR Suntour XCT fork, you can verify this. If you Google that fork specs you will get the axle crown (517mm) and offset (46mm). It is supposed to be 1-1/8” straight threadless steerer.

John

mack_turtle 12-30-20 04:12 PM

any old 1-1/8" fork can fit any modern frame with the right headset bottom assembly.
what is the travel length of the current fork? for a 100mm travel 29er fork, you'll probably want a 480mm or so fork. for a 120mm fork, it might be more like 490-500.

how much are you willing to spend? name-brand carbon fiber rigid forks can cost hundreds of bucks, but a nice steel one can often be found for under $100. lots of used Surly forks out there.

What size is the front axle? depending on the model and year of the bike, it could be 100x9 (conventional quick release), 100x15 (conventional thru-axle), or 110x15 (modern boost spacing).

ft3safety 12-30-20 04:15 PM

Niner makes rigid forks. It may be a little too pricey for what you're looking for:

https://ninerbikes.com/products/nine...t-rdo-mtb-fork

It might not fit either.

iamtim 12-30-20 04:17 PM


Originally Posted by mack_turtle (Post 21855551)
what year is the bike?

Just picked it up a couple of days ago, so probably 2020.

Trail 7 | Trail Bikes | Cannondale


Originally Posted by 70sSanO (Post 21855553)
Supposedly, it has a 100mm SR Suntour XCT fork ... It is supposed to be 1-1/8 straight threadless steerer.

Correct! And that answers my question about the tapered headtube.

iamtim 12-30-20 06:23 PM

So I'm looking for a 480mm, 1-1/8" steerer tube, standard QR axle fork, with drum brake mounts. I'd prefer steel or aluminum over CF... I'm 52 years old and slightly overweight, and I worry about CF forks. I probably shouldn't, but I do. I don't want to spend more than the bike for a replacement fork, so somewhere in the <= $250 mark would be ideal. My google-fu is failing me, and I'm not finding anything to match that criteria.

Any ideas?

Edit: You know, I rode a cross bike for years both on and off-road and it had a CF fork. So disregard the CF comment above, I can use a CF fork if one exists to match.

mack_turtle 12-30-20 07:44 PM

The Salsa Cromoto Grande fork is a nice option might be too short though at 468mm.

70sSanO 12-30-20 09:56 PM

I’m not sure a 468 from a 480 will be an issue for your type of riding. The head angle is 68 and going 12mm shorter might add 1/2*(???).

You can always put a zip tie on the bottom of the stanchion and see how much it moves up (sag) when you are on the bike. Riding a short distance on a really smooth surface will be the best reading of how much fork sag with the way you normally weight the fork.

John

Darth Lefty 12-30-20 10:40 PM

A Krampus or Karate Monkey fork should work too. They are really similar, it comes down to brake rotor size IIRC

IMO you are going on the wrong direction, though.

base2 12-30-20 11:11 PM

I would think you'd want to measure the axle to crown taking into account the suspension sag so that in practice they will ride the same.

The actual rake/trail will change depending on where in the suspension travel is. Bottomed out, for example, would be a steeper headtube angle & the rake would lessen because axle would move some amount of aft when it is telescoped to closer to the crown. How much that is, that would take some math.

Probably a mm or two & a 2 degrees or so. You might download a level app on your phone & place it against some non-tapered part of your bike to measure the actual headtube angle while sitting on your bike in a riding position at the expected sag.

Maybe placing your phone app, squarely on the removed preload cap, or in front of the headtube (assuming non-tapered), or assuming a large bunch of missing headset spacers, on the steerer itself. would get you an accurate measurement.

Placing your bike against a vertical surface such as an outside drywall corner or a kitchen cabinet may be accurate enough with a carpenter square to get the rake. (crownrace center to vertical surface minus axle to vertical surface equals "X")

The point being, if you have a measured axle to crown, & a measured headtube angle, & a measured rake, you can work the rest back to a fork that will be acceptable.

FWIW: Rockshox makes a 1&⅛ straight 700c/29'er air fork with lockout & either 50 or 65mm of travel for ~$250 I think it's called a Paragon. I don't know anything about it, but the lockout may help if you don't find a rigid that works.


Edit: Here is the 65mm one.

freeranger 12-31-20 07:46 AM

If your LBS is a good one, you might start there. They may have access to an inexpensive fork which would work on your bike, and if they know their stuff, will know what works. They may also have switched out a rigid 29, or an inexpensive 29 susp fork with lockout, for a better susp fork on a customers bike, and maybe they could put you into contact with that customer. But I'd start by knowing what specs I need to look for, and if a good LBS, could help with that.

Darth Lefty 12-31-20 01:15 PM

Gotta love the marketing on this thing


PLATFORM:TRAIL

Level Up.

A mountain bike built to raise your game and ignite a passion for the trail. Designed for the mountains and ready for anything.

Where it thrives

Low-impact trails, gravel roads, leisurely ride

iamtim 12-31-20 04:39 PM

So, thanks to an earlier MTB purchase (I'd gotten a Motobecane from BD, but I bought it too big) I had a one-step up from the stock SR/Suntour fork. This one actually has lockout, whereas the stock one did not. Having lockout will suffice for now, until I can afford an upgrade to a better fork.

(I thought that the Motobecane had a tapered head tube, but after tearing it apart I discovered it did not. Yay for me, as that made it compatible with my new bike.)

Thanks for all the replies and advice, I learned a bit about MTB forks that I previously did not know (again, previously I was a former BMX racer and road cyclist, current big-wheel BMX rider).

gsa103 12-31-20 06:21 PM

Suntour has a really good upgrade program. If you're ever inclined you can upgrade the stock fork to a proper air fork like an XCR32 Air or Raidon for about $200. I would strongly recommend that over spending an equal amount on a rigid carbon fork. Good air forks are great, entry level coil forks are just anchors.

freeranger 01-01-21 11:44 AM


Originally Posted by iamtim (Post 21856925)
So, thanks to an earlier MTB purchase (I'd gotten a Motobecane from BD, but I bought it too big) I had a one-step up from the stock SR/Suntour fork. This one actually has lockout, whereas the stock one did not. Having lockout will suffice for now, until I can afford an upgrade to a better fork.

(I thought that the Motobecane had a tapered head tube, but after tearing it apart I discovered it did not. Yay for me, as that made it compatible with my new bike.)

Thanks for all the replies and advice, I learned a bit about MTB forks that I previously did not know (again, previously I was a former BMX racer and road cyclist, current big-wheel BMX rider).

Glad you got something that will work for ya! I had thought of the Suntour exchange program, but when I checked out was was available, they were all tapered steerers, at least that is all that I found.


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