Need Help with Dimensions for USD conversion

60 replies to this topic
  • jesusgatos

Posted February 23, 2007 - 09:06 PM


I've been looking into doing a USD conversion on my XR650R using CRF450 forks. I've read through all the threads on Thumpertalk that I could find about this conversion and there are a lot of posts by people for / against this modification. For now I'd like to side-step any further discussions about whether or not it's a an upgrade or a downgrade. I just want to get a better idea of how any differences in dimensions / geometry between different forks and triple clamps might affect the bike's handling.

I know that Emig Racing makes custom triple clamps specifically for this conversion and they look awesome, but are those triple clamps just made to CRF specs or have they modified the triple clamp geometry to work better on an XR650R? If it wasn't 8:30pm on a Friday evening, I'd just call them and ask.

Emig Racing makes a great looking set of triple clamps and they are selling them at a fair price, but if I decide to do the USD swap I'd like to design my own triple clamps (no real reason except that I'm a DIY type of guy). I'm thinking that I'll incorporate some type of an integrated sub-mount steering damper and I really like RG3's 4-post insulated bar clamps.

So here's what I was able to find on Honda's website

Wheel Travel
00 - 06 XR650R = 11.2"
XX - 07 CRF450X = 12.4"

00 - 06 XR650R = 27.8 degrees
XX - 07 CRF450X = 27.28 degrees

00 - 06 XR650R = 4.3"
XX - 07 CRF450X = 4.4"

00 - 06 XR650R = 58.3"
XX - 07 CRF450X = 58.2"

This is what I haven't found out yet

Offset at the Triple Clamps
00 - 06 XR650R = ?
XX - 07 CRF450R/X = ?

Offset at the Axle
00 - 06 XR650R = ?
XX - 07 CRF450 = ?

Fork Length
00 - 06 XR650R = ?
XX - 07 CRF450 = ?

Outer Diameter of XX - 07 CRF450 Fork legs (at triple clamps)

I'll measure the length and offset at the triple clamps / Axle on my stock front end this weekend and edit this post to include that information.

rmhrc630 never really got much of an answer when he asked about fork offset. RG3 lists 20mm and 24mm triple clamps for 02-07 CRF450 applications and BRP offers triple clamps to fit 00-07 CRF450's with stock (what's that?), 20mm and 22mm of offset. I can't find any companies that manucafture triple clamps for XRR's with different offsets, so I've got to assume that the stock geometry works pretty well. I'd just like to figure out what type of geometry I'd need to design into these triple clamps to mimic the stock geometry.

Here's some good info that I found while researching this swap:

Adapting CRF450 forks to XR650R using CRF triple clamps

This web page outlines one way to modify Honda CRF 450 triple clamps to fit an XR650R.

In this thread, Blakerj10 posted an alternative to that approach:

I left the stock CRF stem in the stock CRF lower clamp. Went to my local machine shop and he machined the top of the steering stem to the same outside diameter of the top of the xr steering stem. Now I could use the stock upper xr bearing. Then for the upper crf clamp, he made thin sleeve to slide between the now narower steering stem and upper clamp.

In this thread ESS also suggested that,

If you are putting on a newer CR or CRF front end you don't need to swap the stem. Call a guy named Rob at this place . He has the upper bearing and race to make the CR or CRF trees work. The lower is the same as the 650's so all you need is the upper. I think there is a different washer to go with it too. Ask him about that also. $60 for bearing and race. Pop out your old race, install the new one with the new bearing, then just grind the steering stops on the lower tree to get your desired turning radius.

Other Relevant Links

USD 47mm Showas installed

Xrr + USD = ?????

CR/CRF forks on a XR650R

XR 650 inverted fork?

xr fork conversion

USD forklegs?

650R USD fork valving/spring set up

  • jesusgatos

Posted August 08, 2007 - 04:44 PM


UPDATE: I've got a CRF450 front end on my bike right now using a stock lower tripleclamp and an older Pro Taper upper tripleclamp so I can run 1 1/8" bars. Not real happy with this current setup.

Purchasing all the parts for the swap was a major pain in the ass. I buy and sell a lot of stuff online and generally do alright, but I got burned pretty bad buying these particular parts (for the record, John Mercer is a thief).

I bought a modified upper CRF upper bearing from Evolution Suspension. This was convenient because it allowed me to just bolt-on the entire CRF front end, but I wouldn't choose to do it that way again. The race is machined down so much that getting this upper race out is going to be a nightmare. There's just nowhere to seat a punch. The only way I can see removing it (without grinding on the inside of the headtube) would be to weld a small piece of steel to the race and then drive THAT out.

In hindsight, I would have been much better off using the XR650 stem, machining a little bit of material off of the upper tripleclamp (to make the thicker CRF tripleclamps work with the shorter XR stem) and pressing a machined bushing into the upper tripleclamp (to make the CRF tripleclamp fit the smaller diameter XR stem). A machine shop wouldn't have charged me much more than $60 for that work and I would have been able to use a stock XR upper bearing.

Modifying the steering stops was easy enough, but I'm not really happy with how that turned out either. The steering stops on the CRF lower tripleclamps don't contact the stock steering stops on the XR frame; they hit the extra lump of material on the front of the headtube. It works alright, but it's pretty hacked and my turning radius isn't as good as stock.

I also ran into a problem with the front fender that I hadn't read about. The fender mounts on the XR tripleclamp are located about 9.5mm's further forward than the fender mounts on the CRF tripleclamp. As a result, the back of the fender didn't clear the frame. I had to trim the back of the CRF fender quite a bit (supermoto style) and it still rubs just a little bit.

The bottom line is that I don't think this swap is worth doing without using tripleclamps that were custom-made for the CR/CRF conversion. I put this front-end on my bike to see how it would all go together and now I have a much better idea of what I need to build to do it right.

  • Blakerj10

Posted August 09, 2007 - 10:12 AM


For the front fender issue, I placed one washer between the fender and the lower clamp on the two rear fender bolts. Works perfect and can't even tell they are there.

Offset... It must be different (I never measured it), because it does handle different.

Overall, this mod makes the bike better at what it was poor at before, but it is a compromise for what it excelled at before. Kind of takes the bike out of its niche and places it in spot where it is not the best at anything, but still can do most things decent.

Now that my stable has grown, I think this bike is going to get lowered and used for ice racing primarily. I think the stiff fork and offset forks should work well for that purpose.

  • jesusgatos

Posted August 09, 2007 - 10:59 AM


For the front fender issue, I placed one washer between the fender and the lower clamp on the two rear fender bolts. Works perfect and can't even tell they are there.

Huh, I tried fitting the stock XR fender and a CRF fender and they both would have needed to be shimmed quite a bit more than that.

Offset... It must be different (I never measured it), because it does handle different.

The offset at the tripleclamps is the same (24mm's), but the offset at the axle is different. The stock XR axle is located about 37.75mm's in front of the forks (measured center-to-center) and the CR/CRF front end is only 33.25mm's. I'm almost finished drawing the new set of tripleclamps and right now they're at 24mm's offset, but I think I'm going to push the offset forward a few more mm's to make the CRF front end feel more like stock.

  • ESS

Posted August 10, 2007 - 12:58 AM


Sorry to hear about your problems jesusgatos. Now I feel as if I steered you wrong. The $60 vs $525 was a no brainer for me. The bearing and race work just fine for me. The washer supplied by evolution suspension doesn't compromise the front end at all. It just raises the clamp to the correct height. Once the pinch bolts and stem nut are tightened it is solid as a rock and looks like factory stuff.

The steering doesn't turn quite as much, but I never need to turn it that much unless I'm parking the bike and rolling it around in the garage. A little turn on the bars and a little lean and you can make all the turns you need too. As far as the front fender, Blakerj10 is right. I used a CRF450 front fender and put 1/8 inch washers on the two rear bolts. No hitting, and no cutting as you can see in my pics. Maybe I should have taken some close ups of the stops and the fender mounts.:excuseme:

  • Blakerj10

Posted August 10, 2007 - 01:13 PM


Wow, 4.5mm difference in the axle huh? I guess that would account for my interpretations of the handling characteristics. Maybe I should get one of those eccentric axles and try to fudge it back closer to XR specs... That might just be the ticket. Even if it does not get it back 100%, it would be great to change the axle offset for ice races.

  • jesusgatos

Posted August 13, 2007 - 11:28 AM


I wasn't trying to say that you gave me bad advice. I just wanted to post my thoughts on that because I thought it might help other people when they're researching the swap.

As far as the fender goes, I don't know what to say. I tried the stock fender, a CRF250X fender and a CR125 fender. They all fit about the same and I would have needed to shim each of them about 1/4". Glad to hear that setup is working for you.

I'm almost finished designing the new set of tripleclamps and I'm planning to push the offset forward a few mm's (maybe 26mm?) to compensate for the differences in offset at the axle. The CR/F forks are a little over an inch longer too, so I think I'll try to figure out how long each set of forks are at static ride height and see how much the length and offset affects the wheelbase.

The steering stops are also in the right location, so they'll contact the frame in the right spot and should allow the full range of steering. The only thing that might affect the turning radius is the Unabiker rad guards that I special-ordered to fit the thicker Fluidyne radiators. I might have to trim those or rework them a little bit.

I've already pushed the fender mounts forward so they're in the same location as the stock XR tripleclamps, so the fender will fit without trimming or shimming.

Right now I'm modifying the upper tripleclamp design so that it will work with a SUB-mounted SCOTTS steering stabilizer and the SCOTTS forward-mount stabilizer post.

I'll post some pictures of the tripleclamp drawings as soon as they're finished.

  • jesusgatos

Posted August 13, 2007 - 12:00 PM


By the way, what kind of turning radius should I shoot for? The SCOTTS stabilizers seem capable of about 47-48 degrees (each way) and my WR locks up at about 45 degrees. I forgot to measure the stock XR650R tripleclamps before I took them off. What about the CR/F's?

  • eastreich

Posted August 14, 2007 - 11:40 AM


I am using a BRP upper clamp for a CR500 (OEM CR500 lower) on my 650R, and I agree with the complaints of the seeming lack of turning radius. However, with my forward mounted Scotts, I don't have any more room as at full lock the stabilizer tower has maybe .5 mm clearance with the upper clamp.

I agree with what was mentioned in the previous post about the improvements of the stiffer forks. There are some positives, but also some negatives. As for the balance, when I switched to the CR500 shock body I gained about 1/2 inch in shock shaft length (I used the stock CR seal head with the 650 shaft). This increase in rear ride height seemed to really help re-balance my 650. I have no complaints anymore about the handling. Now it is a win-win situation with the USD forks.

  • jesusgatos

Posted August 14, 2007 - 12:01 PM


I know what you mean about clearance between the upper tripleclamp and the forward-mount stabilizer post. Nick at BRP told me that the XR650R goes 80 degrees lock-to-lock, so I designed the upper tripleclamp to clear the forwad-mount post at 40 degrees (off-center). I just finished the blueprints and will post some pictures in a few minutes.

I also just picked up a CR500 rear shock and a Gold Valve fron Race-Tech. I'm going to re-valve the rear shock and the front fork at the same time.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • jesusgatos

Posted August 14, 2007 - 02:53 PM


Here are a few pictures of the tripleclamps that I've designed.

Posted Image

Posted Image

Posted Image

Posted Image

The design was mostly dictated by the dimensions, but this was a pretty interesting game of conect-the-dots because I was trying to make a lot of things work together. The Emig tripleclamps look really nice, but they only work with their steering stabilizer and I would rather run a SCOTTS. Plust Emig only offers them with a 24mm offset and I would prefer something that was closer to the stock effective offset (combination of the offset at the tripleclamps and the front axle). Anyway, here are the highlights:

  • works with SUB-mounted SCOTTS stabilizer AND forward-mount stabilizer post
  • full range of steering (80 degrees - same as stock)
  • offset at tripleclamps adjusted to mimick stock geometry
  • handlebar mounts are reversible offer 6mm of adjustment (11mm/stock & 17mm forward)
  • no fender clearance issues
  • 184 grams lighter than stock CRf tripleclamps (not counting handlebar mounts or steering stabilizer)

There are a few things that I still need to finish though:

  • I have to measure the fork lengths and wheelbase and finalize the offset.
  • I would like to run rubber-mounted handlebar clamps, but there are a few clearance issues that might be a little difficult to resolve
  • I'm also going to incoporate some type of handguard mounts into the handlebar clamps along with a built-in mount for a Trailtech computer

So, what do you guys think?

I've been talking to Steve at SCOTTS over the last few days about the possibility of them adding these tripleclamps to their product line. If you would be interested, let them know by replying to this thread.

  • eastreich

Posted August 14, 2007 - 03:23 PM


Those look great! The only thing that I would change, and maybe this is just me, but I would locate the pinch bolts on the upper clamp on the leading edge of the clamps for two reasons:

#1 is that with the bolts angled on the rear of the clamps there may be clearance issues with a large tank (as in the bolts contacting the tank).

#2 is that with the pinch bolts on the leading edge, you could use one of the standard Cycra triple clamp mounting systems for their handguards. Of course, if you have the solution mounting system, or OEM style handguards, this is a non-issue.

If I was ever going to switch to the Showa CRF forks over my KYB's I would definitely consider purchasing a set of these from Scotts if they made them!

  • jesusgatos

Posted August 14, 2007 - 03:43 PM


Thanks for the feedback.

The clearance at the tank is a valid concern, but I'm running an IMS 4.6 gallon tank and it 'looks' like they'll clear just fine. The pinch-bolts on the lower tripleclamp need to be where they are so they'll clear the radiator guards at full-lock and I think it looks pretty nice having the upper pinch-bolts in the same location. I wouldn't put them there for looks alone, but I don't really see a downside.

As far as the handguard mounts, I HATE the Cycra tripleclamp mounts that I'm running on three of my other bikes. They just fold inward and get bent out of shape way too easily. I purchased a Solution mount for my 650 and after installing it, I've decided that those extra brackets are kind of redundant. So I'm going to build the inner handguard mounts (for a set of ProBends) into the handlebar clamps. I think integrated handguard mounts are the way to go. I'll post some updated screen captures of what that will look like.

  • eastreich

Posted August 14, 2007 - 06:03 PM


I have used all the different methods for mounting the Cycra's as you have described and completely agree with you. I am running the solution mounting currently, but I just don't really like that setup, either. I can bend the guards up quite easily.

I am planning on building a custom lower handle bar mount that will accomodate the Cycra's. I already have the design for my setup drawn up, but as I am using a BRP CR500 upper clamp, my setup is pretty specific, unlike the design you are working on. I have already had to re-machine the upper half of the BRP mount to allow for my Scott's to mount in the forward position.

I forget that you are increasing the offset of the clamps, which will allow for the location of the pinch bolts as you have them. My bad! :bonk: I really like the "wrap" style that you have drawn up; it adds that little extra bit of style that you can't get with other parts.:thumbsup:

  • ESS

Posted August 15, 2007 - 12:37 AM


Those look great. If the price was right I'd think about switching. The only bad thing is the upper pinch bolts don't allow for the Electrosport (Dakar) dual sport kit to be installed. I'd have to switch dual sport kits also. That would throw off the price range for me.

  • jesusgatos

Posted August 18, 2007 - 01:21 PM


Here are a few more screen-captures that show how the SCOTTS forward mount stabilizer post works with these tripleclamps. These all show the steering at full-lock (40 degrees off-center) to the right.

Posted Image

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  • martinfan30

Posted August 19, 2007 - 08:00 AM


go here

  • Potts228

Posted August 19, 2007 - 08:13 AM


I know what you mean about clearance between the upper tripleclamp and the forward-mount stabilizer post. Nick at BRP told me that the XR650R goes 80 degrees lock-to-lock, so I designed the upper tripleclamp to clear the forwad-mount post at 40 degrees (off-center). I just finished the blueprints and will post some pictures in a few minutes.

I also just picked up a CR500 rear shock and a Gold Valve fron Race-Tech. I'm going to re-valve the rear shock and the front fork at the same time.

Are you going to use the XR650R shock shaft on the CR500 shock?

  • BWB63

Posted August 19, 2007 - 08:58 AM


I am running the CR500 shock with the XR650R shaft and shim stack. I found that the low speed compression ajustment range is different on the CR500. I went with a little stiff compression stack on the compression shim stack and it put me out on the far side of the adjustment screw. With 2.5wt Golden Spectro Ultra Lite Suspension fluid and a CR500 Gold valve, I have the compression adjustment all the way out and it is almost enough. The Baja 500 shim stack on seems to be the ticket. I am going to the Setup that says CR500 shock setup. I am thinking of going to CRF450R forks also dew to the fact that the hybread CR500/XR650R shock raises the rear about an inch. It is hard to get the right rake back with the stock forks.

  • jesusgatos

Posted August 19, 2007 - 10:53 AM


Thanks, I've read all of your posts about the CR500 shock swap and I was planning to post a few more specific questions for you when I get into that project. My Gold Valve just showed up, but I still need to order shims.

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