250r forks vs 350x fork length Q

[Troyg25]

Just wondering how the 250r second gen forks compare to the 350x forks? Are they the same length? Would a 85 250r set up work on a 350x?

Any info on lengths would be helpful.

Thanks

[onformula1]

The 83-84 250r forks are 50mm shorter than the 350x when on a trike.

The 83-84 250r fork sliders are longer, but the lenght is on the underside of the axle.

Both have 35mm tubes, using the 83-84 250r damper rods in a 350x will give you .7 in. of extra wheel travel on the 350x forks.


Using the 250r tubes will only give you shorter forks by 50mm.


The 85-86 250r forks are 39mm, the problem is they are trailing axle, if you use the 250r triple clamps it will work but the geometry will be thrown off and will not handle correctly with out major mods.

The 350x triple clamps are not large enough to be safely bored to the larger 39mm 250r fork tube size, but it doesn't matter because you still have trailing axle issue.

The 350x forks are the way to go on a 350x, unless you want to go the MX forks, but that is a whole different can of worms.

I have been performing some serious mods with the 350x forks with great results, one set with be on the boards soon on a very, very trike MX racing trike!

[Troyg25]

Thank you for answering that. Lots of great info and specific details. Just exploring my ideas and how to build my 350x. It only makes sense to use only the 350x set up.

Thank you

[onformula1]

No problem, you're welcome.

Check and make sure the fork tubes are straight, the last three sets I have seen only had 1 out of 6 straight tubes.

[barnett468]

.
Lots of good info above but if you plan on using longer damper rods, you need to check how much if any play you have between the fork tube and lower leg at full extension because any play you have will be increased a bit by doing this.

I had this problem on one of my race bikes I did this to back around 1975 when Dallas Baker used to sell extended rods so I had to take them out . . Didn’t seem like a good idea to have floppy forks on the infamous downhill at Carlsbad Raceway.

If your fork springs are too soft, you can buy heavier springs for them . . A few different mfg’s make them . . Below is just one mfg of them . . They also have an online spring weight estimator and they have several different spring rates . . They also make a special valve for the forks and rear shock called a gold valve emulator which improves the damping a bit . . It’s basically a similar design to the valve Works Performance designed many years ago for their own shocks, but they designed it to so it could be “retrofitted” on some bikes…pretty cool.

http://racetech.com/ProductSearch/3/...TC350X/1985-86


If your fork springs are soft and you just need a temporary fix, you can preload then around 1” with a piece of pvc tubing or metal pipe but this will only help a little so you can also add around 10 psi of air to your forks thru the valve on top of them if your fork seals aren’t leaking . . You might try some heavier fork oil also.

[barnett468]

.

Just exploring my ideas and how to build my 350x. It only makes sense to use only the 350x set up.

well if you are going to build it to higher perf specs heres some ideas.


Frame gusset kits.

These guys make a lot of custom parts including billet cnc’d tripple clamps and extended swing arms.

http://www.hreatv.com/custombuiltparts.html

http://www.hreatv.com/productionparts.html





this is a different company but i don't know if they are still in business.

http://www.tpctrikes.com/tpctrikes_102.htm

[Red Rider]

Both sets are leading axle.

All 250R's were trailing axle, '81-86.

[onformula1]

All 250R's were trailing axle, '81-86.

True, but not on my work bench...LOL!

it's been a long day, brain fart.

Thanks, Edit.

[oscarmayer]

Just so everyone is clear, Onformula1 actually has several sets of each type of fork sitting on the bench that I supplied him for test and dev. work. When he states some specs, it's from physical measurements. He has the parts right there in front of him physically not reading or guessing (no offence to anyone at all, I just know how the internet can be). So please understand he is giving you physical facts on these parts.

Yes the 250R forks are trailing, but the rake from factory is slightly more than the 350X so they are equal to or extend past the 350x front footprint when done. Hope this helps clear up any confusion.
Good thing we are discussing what will work best for pieces mixed and matched and really debating what is a better fork. that is a completely different animal!

I stated before and will state it again. Racetech is great "out of the box" stuff, but when your wanting more than basic riding and want lots of room for adjustment to fine tune your style, you need custom. The costs of having a builder do a racetech setup Vs. having a custom one from Onformula1 is very close. So guys think about it. before you spend a lot of $ on stuff decide what you need and talk to him. He really does know his stuff. That is why he is handling all my suspension needs.

[Red Rider]

True, but not on my work bench...LOL!

I see. So, you were talking about a modified set of 350X/250R forks that are leading axle. When I read your post, it didn't come across that way to me. Sorry.

[Dirtcrasher]

I ran 250R forks in my 350X. I believe when I spun them around from the 250R mounting perspective, the rake was pretty close to stock. About a 12mm difference measuring the center of the axle to the footpegs.

I had to press a 350X stem into the R clamps. I believe I had to bore it on my Bridgeport. And you have to move the tank back an inch or the R forks hit your shrouds. Bill at TPC taught me how to do the conversion.

I did it, I rode it and they were a nice improvement. However, some of those modifications aren't for the average Joe.

In truth, The inverts are the way to go, I absolutely love them and they are complimented by a custom AXIS shock making it a great suspension package!

Not cheap though!!