Possible to put on a 21" wheel on a CRF150R fork?


13 replies to this topic
  • Nigel Tufnel

Posted March 06, 2008 - 01:40 PM

#1

Anyone know if it is possible to put a standard 21" front on a CRF150R/CR85 fork? Enough clearance between bottom crown and top of wheel when the fork is fully compressed?

I am inquiring because of a frankinbike I am concieving.

  • trailrider9

Posted March 06, 2008 - 01:46 PM

#2

you might could if you slipped the forks down in the clamp so that the top of the fork is flush with the top of the upper triple clamp. and yes it is fine to do this because i did it on my 150rb along with tightening the sag on the rear spring to raise it up a little.

  • armourbl

Posted March 06, 2008 - 02:30 PM

#3

I wouldn't recommend doing this. You are going to change the steering geometry of the bike drastically. Not to mention if the wheel bottoms out on the fender it will be the same as locking the front brake.

Why would you want to put a 21" wheel on anyways?

ben

  • Ghini

Posted March 06, 2008 - 02:32 PM

#4

idk about your question, but i love frankenbikes, what do you have in mind?!

  • Nigel Tufnel

Posted March 06, 2008 - 03:25 PM

#5

Why would you want to put a 21" wheel on anyways?

ben


As I indicated in my original post, I am contemplating a frankinbike. I want to make an adult sized version of the CRF150R that weighs 160lbs.

  • armourbl

Posted March 06, 2008 - 03:28 PM

#6

Probably would be cheaper to put the engine in a 125 frame. Especially if you found an older model you could pick up real cheap.

ben

  • yz440e

Posted March 06, 2008 - 07:31 PM

#7

Well I think your biggest problem would come from the hubs. No one makes 21" spokes for a 150r hub, the front and rear axle diameters on big bikes are substantially larger than 150 axels. The only way I could see you doing it would be using a big bike hub and sleeving down the diameter to the correct diameter, then having custom wheel spacers machined. Also swing arm clearances could be a problem (if it did work with stock RB length swing arm, you would have no chain adjustment.) As far as clearances go with the fenders (assuming you want to do a 19" or 18" rear) I think that is the least of your worries, you can always do trimming and modifying to the body work to make it work...Post pics if you get it to work!

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  • steepisgood

Posted March 06, 2008 - 07:51 PM

#8

I have the 18 drum rear and 21" front for sale from a 04 crf 230f, and I think the front fits...

any know for sure.

let me know,

edwin

  • 4strokeridertt

Posted March 07, 2008 - 08:50 AM

#9

Easy fits no problem. Reger Engineering makes the axle spacers and brake adapter for the CRF150RB or CR85RB. You will need a CRF230 front wheel complete and a CRF150F or 230F caliper to fit the rotor so you can stop. I don't have a clue on the rear.
The short wheel base may be a problem at higher speeds, you know a bit wild but not unridable.

  • oswa

Posted April 26, 2009 - 10:09 PM

#10

Thanks for the Reger Engineering link!
Anybody know of a solution for the rear? I'd like to get an 18" rear wheel in.
I saw pictures of swing arm 'externders' but I have not been able to locate anybody that actually sells them, ideas?

Thanks

  • G31m

Posted April 27, 2009 - 06:11 AM

#11

I want to make an adult sized version of the CRF150R that weighs 160lbs.

A noble goal, to be sure, but probably not doable.
By the time you add the bigger wheels and tires and a longer swingarm to accommodate the larger rear wheel, you'll be up beyond the advertised dry weight of 165+ pounds for the CRF150R.
What do you hope to accomplish with the 21/18 wheels/tires??
Changing the wheel diameters will not make the bike "adult-sized"...the chassis (seat-to-handlebar-to-footpegs) is still scaled for children.

The suggestion of putting the 150R engine in a 230 chassis makes the most sense....then spending another $4000 on lightening the bike to get it below 200lbs would acheive your goal, maybe? A full sized dirt bike weighing 160lbs? ....maybe a low speed trials bike with spindly frame and suspension components.

G31m

  • oswa

Posted April 27, 2009 - 02:38 PM

#12

A noble goal, to be sure, but probably not doable.
By the time you add the bigger wheels and tires and a longer swingarm to accommodate the larger rear wheel, you'll be up beyond the advertised dry weight of 165+ pounds for the CRF150R.
What do you hope to accomplish with the 21/18 wheels/tires??
Changing the wheel diameters will not make the bike "adult-sized"...the chassis (seat-to-handlebar-to-footpegs) is still scaled for children.

The suggestion of putting the 150R engine in a 230 chassis makes the most sense....then spending another $4000 on lightening the bike to get it below 200lbs would acheive your goal, maybe?

Well, I didn't start the thread so I don't know what the original poster's intent was, but I'll explain mine.
I want to create a decently trail friendly, lightweight bike that my SO can ride.
She already rides the 150 quite well, but a full-size wheel combo would make it a better trail bike.
Modifying a 230 is not an option. That's what we started with.
It's heavier, lacks power and the suspension is quite useless.

Putting a 21/18 tire-combo on the 150 would as you pointed out not solve the rider ergonomics, but it will create a hybrid that will allow her to ride a bike with a good power to weight ratio and real suspension, without the weight and full-height of a 250.
We've done what we can with riding ergonomics already and while it's never going to be as good as a full size bike it's good enough for the time being.

  • G31m

Posted April 28, 2009 - 05:30 AM

#13

Putting a 21/18 tire-combo on the 150 would as you pointed out not solve the rider ergonomics, but it will create a hybrid that will allow her to ride a bike with a good power to weight ratio and real suspension, without the weight and full-height of a 250..



The stock CRF150R has good power/weight ratio and real suspension as is. Not sure what going to larger wheels would do to improve that, nor will it improve rider ergonomics....so, what is the point...other than to add weight and height??
Not trying to rain on your parade, oswa, just trying to get inside your mind and find out what your train of thought is.....
I'd love to have a CRF150R that had footpegs an additional 4" back and down, with the same seat height, but it would take a different frame to achieve that...a frame that would have to give up ground clearance and quickness of handling.
Everything in life is a compromise, eh?

G31m

  • oswa

Posted April 28, 2009 - 07:45 AM

#14

The stock CRF150R has good power/weight ratio and real suspension as is. Not sure what going to larger wheels would do to improve that, nor will it improve rider ergonomics....so, what is the point...other than to add weight and height??
Not trying to rain on your parade, oswa, just trying to get inside your mind and find out what your train of thought is.....

No problem.

It's largely a confidence thing.
I'm positive I can get the girlfriend on the 150r with 21/18 and get her to ride that bike in single track even if she doesn't flat-foot it.
She should be riding a full size 250, but she's not comfortable doing so for two main reasons: height and weight.
I'm trying to get as close to a 250 as I can without getting one.

As you know the 21/18 combo would do nothing for the power to weight ratio. I made that comment regarding comparing the 150r to a 230.
What the 21/18 wheel combination would give me is the ability to roll over bigger obstacles without 'problems' . It will also raise the ground clearance somewhat.
The smaller wheels of the 150r makes it harder to ride in choppy (think rocks and roots) terrain as the obstacles are larger, relative to the wheels than if it had a 21/18 combination.

I'd love to have a CRF150R that had footpegs an additional 4" back and down, with the same seat height, but it would take a different frame to achieve that...a frame that would have to give up ground clearance and quickness of handling.

You and me both! :banghead:
I regularly use the 150r as a playbike, but I can't ride it very long due to the ergos. Even with risers, taller bars, seat etc it's far from good for an adult around 5'11".
The engine and suspension in a slightly larger chassie would be one hell of an adult playbike/learner.





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