Wheels & Tyres

[knackeredMk1]

There is a lot of information that can be found by doing a search on this site but the basics are:

All CRM wheels will fit all CRMs except the front wheel on a Mk1 which has a 15mm spindle - Every other model has a 17mm so bearings, spacer and seals need to be swapped.

XR400 front wheels fit straight on Mk2/3/AR but XR250R front wheels have a 15mm spindle like the Mk1 (and will fit Mk1s). XR400 and XR250R rear wheels fit straight on all CRMs.

I believe that XR600 front wheels are like the XR250 and CRM250 Mk1 and have 15mm bearings.

XR650 front wheels are a direct swap for all but Mk1s, but the rears need a change of bearings and seals. The rear also needs a disk change that requires some alteration to the attachment points - but easily done.

CR/CRF wheels can be fitted and depending on the original specifications need bearing &/or spacer(s) &/or seals replacing. Early 90s wheels are likely to go straight on but the spindle sizes have changed several times since then. The condition of early 90s wheels may not be good.

The speedo drive from a Mk1 will not fit later Mks due to spindle size difference.

[knackeredMk1]

As mentioned above XR400/250 wheels will fit subject to the Mk1 spindle size issue.

Other road going wheels can be altered if you have the skills/money. A favourite seems to be the Cagiva Mito/Planet/Raptor.

On the rear 140 width fits straight on but if you use a 150 rear tyre you sometimes (depending on tyre) have to remove the chain guard (the tag on the inside of the swing arm) and space out the front and rear sprockets slightly to avoid the chain catching the rear tyre. Fitting a non-O-ring chain will help but using spacers (2-3mm) to pack out the front & rear sproket will probably be necessary. Front 120/70 is fine.

You can respoke CRM wheel hubs to fit 17 inch rims provided the rims have the correct number of spokes.

[knackeredMk1]

All road legal tyres will have an 'e' mark.

Offroad -

Rims

Front – 1.60 x 21”

Rear - 2.15 x 18”

Tyres

Profile

Don’t get hung up on the 70/80/90/100 part in tyre sizing. Manufacturers dictate what this is so whilst it does mean something (profile/sidewall height) it's not important to us average riders. The higher the number the deeper to tyre wall.

Width

Rear Motocross

100 - This is really a 125 tyre.
110 - Best for CRM
120 - these are quite rare but suit 450s and 500 2 strokes in dry conditions. Even a 65BHP 500 works better on a 110 in the wet.

Rear Enduro

120 - This is really a 125 tyre though some people like it on a 250 4 strokes (especially if it's wet).
140 - Best for CRM
130 - Michelin did make a 130 (not sure if it's still available) Would suit CRM.
Beware that not all manufacturers give the same measurements e.g. Mitas C-02 says 120 width though it is actually as wide and has deeper knobs than other 140s.

Front

Just buy a tyre you get on with/can afford – they’re all essentially the same size.

You also have to take into account the terain you are going to ride on. e.g. Tyres suited to wet/muddy going are going to be very slippy on rocks. Tyres suited to hard terrain are not going to last long on the road but will give more grip on the road/rocks.

[knackeredMk1]

XR 650 wheels tend to be cheaper than the direct fit options and also tend to be in better condition. A lot of them have been removed soon after the owner purchased the bike so as to be able to fit SM wheels.

As has been stated elsewhere XR 650 front wheels are a straight swap for all CRM 17mm spindle wheels.

The rears can be swapped but the following changes need to be made:

The brake disk is too large so a CRM one has to be fitted. This necessitates changing the disk bolt holes. They need to be drilled and tapped to take CRM M8 bolts and neeed a small M10 recess to accomodate the collar on the CRM bolts. This recess is ~ 3mm deep.

The XR wheel originally has a 20mm spindle so the bearings and seals need changing. The bearings required are:

1 x 6303 2RS - (17x47x14mm)
1 x 6302 2RS - (15x42x13mm) This bearing has a 15mm internal diameter and needs boring out to 17mm. Your bearing supplier should be able to do this.

Seals are:

1 x 25x42x7 R23
1 x 24x47x7 R23

These will fit over the standard CRM spacers. In theory you need to take 1mm off the brake side spacer but in reality you don't as there is enough 'slack' in the tolerances to allow you not to do this. However don't be afraid to do a little bit of filing if you find it is necessary.

You will also need to make an internal spacer to fit between the bearings in the hub. 17mm internal diameter & ~ 24/25mm outside diameter but the same length as the original that was in the wheel.

You can get wider bearings (eg 623032RSRC3 17x47x19mm) to fit in the drive side space for more durability but you have to compensate for this extra width by making the spacer thinner.

[knackeredMk1]

Standard wheel bearings/seals are:

Rear all Mks - 1 x 6203 2RS + 1 x 6303 2RS. Seals Mk2/3/AR - 1 x 25x40x7 + 1 x 25x47x6.5 Seals Mk1 - 2 x 25x40x7.

Front Mk1 - 2 x 6202 2RS. Seals - 1 x 21x37x7 + 1 x 40x50x5.
If you want to put a Mk1 or XR250 wheel on a larger 17mm spindle you will have to get the same bearings and seals as for the other Mks. You may be able to get away with the spacers from the other Mks but I don't know. You may have to get new width spacers made up.

Front Mk2/3/AR - 2 x 6003 2RS. Seals - 1 x 24x37x7 + 1 x 40x50x5.

[knackeredMk1]

This wheel looks fine bit of local surface corrosion on rim but very good stainless spokes and nipples (Hub is good too) -



Check again, it's as rotten as a pear . What you see is just powder ~ 6mm deep -





Please, Please use rubber rim tape and not duct tape. It really messes things up . All for the cost of £1 each..................