Hi,

I've been messing around with swapping a rear wheel from a nc30 into a nc24, mostly because the tiny rear in the nc24 (combined with an old - old tire) deeply worried me when I took it to Mallory, and partly because I managed to get a nc30 rear with a decent tire cheap on ebay. I did then end up buying a load of other NC30 bits to make it work which I didn't intend on doing originally, but never mind. I've highlighted in red all the new parts below.

I think there are other ways of doing this involving re-machining a NC30 rear axle, but I thought this was easiest as it didn't involve re-machining or grinding a bearing running surface on the axle.

Bear in mind that if you do this it does change the bikes handling, partly because of the rear tyre width, and partly because the rear of the bike ends up a bit higher. I thought it was an improvement, but others may not agree. Also it gets rid of the cush drive.

The 4.5" rear from a nc30 just fits with enough clearance between the swing arm and the exhaust.

It went something like this...

slacken chain, remove axle nut and cush drive (Mine required rather a lot of persuasion – had to split the nut in the end).

remove rear brake caliper and bracket (large awkward circlip)

remove rear wheel, brake and axle from nc24

remove rear hub (both clamp bolts need to be out to do this)

gently (without damaging the hub – I completely wrecked the original bearing doing this, but the hub was ok) remove needle roller bearing from hub (nc24 is 48mm id needle roller bearing).

re-machine hub needle roller bearing cir-clip groove (make wider by 2.5 mm if I remember correctly) to install nc30 (62mm od, 50id) needle roller bearing. This bearing is slightly longer, hence the need to re-machine the cir-clip groove.

Check the height of the NC30 rear brake bracket – either re-machine the external circlip groove (make longer by about 2mm) or remove material from the nc30 brake bracket to make the step / boss in it less high. I went for the first option, as I have a lathe but not a milling machine.

Gently (i.e. without damaging anything) fit the new bearing and old circlip into the newly machined NC24 hub. Install new NC30 rear bearing Dust seal (50mm ID, 62mm OD).

Fit NC30 rear axle and brake disk (Including separate internal splined shaft) into the hub

Fit nc30 rear brake bracket, using the old torque arm and bolts from the NC24 and the original massive awkward circlip.

Spin the hub so that it is lowest point, as the nc30 caliper won't fit in the hubs original position (at the top). I ended up drilling a few new holes to allow you to spin the hub to adjust the chain, as the normal position for this is for the axle to be above the centre line of the hub (hope that makes sense).

Fit the NC30 rear caliper.

Make a spacer to fit behind the NC30 sprocket carrier (~11mm long), 40mm ID, which clamps up to the original nc24 ball bearing. While all this is going on its probably worth replacing the other wheel bearing too (NC24 rear wheel ball bearing).

Fit NC30 sprocket carrier & nut

Fit NC30 wheel, spacer, washer, and castellated nut onto the splined shaft which sits in the middle of the NC30 axle. I couldn't find an original nut, but made / botched my own from a standard M18 x 1.5mm pitch nut.

And there we go, photos below (hopefully)...

Interesting conversion..

Do you have a pic of the other side? How does it react by comparison to the old wheel? Did you consider changing the front too?

I always liked the '24 albeit different from my '30..

there was a guy on here with a grey nc30 that had an nc24 motor / oil cooler in it but the nc30 rads and cant remember what exhaust, maybe stock (would be off balance on a 24 motor)

id like something like that as the 24 motor is easier to service with the locknut adjustable tappets and larger plugs are cheaper / more readily available.

and yes.. the last person on here to do this mod machined the axle.

You can fit a 140 tyre to the back wheel without issue, its not manufacturer certified from most manufatureres but I know people that used to track-day stock 3.5" NC24 rear wheel with a 150/60/18 on it without any issues and they were pushing pretty hard.

from the rim to tyre application chart

130/60*18 3.00/3.50/4.00
130/70*18

140/60*18 3.50/4.00/4.50
140/70*18
150/60*18
150/70*18


If I remember rightly it was a bt90 on the back and a bt39 on the front perhaps.. I can check if anyone is really interested.

I sometimes think the 24 is over-shadowed by the 30 and 35 models which is a shame as it's a great bike..

I googled NC30 wheels in NC24 images but no returns, just various pix of 24s and 30s so I'm very interested to see the finished thing.

VtypeV4 wrote:I sometimes think the 24 is over-shadowed by the 30 and 35 models which is a shame as it's a great bike..

I googled NC30 wheels in NC24 images but no returns, just various pix of 24s and 30s so I'm very interested to see the finished thing.

Is is let down too much by the brakes forks / rear shock and frame compared to the nc30 when used competitively, as a general streetbike its fine.

I've never tried one on track..

Its at a friends at the moment, I'll stick some more pictures up when its back.

To me, the original rear tire basically felt thin, if you turned in quickly it felt a little bit like you were dropping the bike. Completely fine on the roads, as I don't really do that, just a bit worrying on the track. I think it now has a bt90 on the rear, I'll check that when I pick it up. The wider rear makes it feel like the rear is dropping less suddenly as you lean it over, if that makes sense...? I'm happy with it anyway (got my knee down for the first time on it on another trip to Mallory since doing it) so it can't be too bad.

I did have a bit of a think about doing the front wheel, but I quite like how easy it is to change direction with the little front wheel (16"). Having read about it a little, it sounded like it would be best to change the whole front end, which I don't really want to spend the money on (Ignoring that I have pretty much done this on the back).

I guess you've kinda got the best of both worlds there with the wider and larger rear wheel for stability and the narrow 16" wheel up front for that quick fall in. My only concern would be how much more of the front tyre is being used with the rear now being that much wider. And a radial or course whereas the front is still only a 100? or maybe 110? width cross / bias ply type but having said that, if you're dragging your knee then it must be working well.

Ben used to use Bridgestone BT45s (available in all sorts of funny sizes) on his '24 with standard wheels and they always felt re-assuringly grippy. I use them on the FJ too and are great although they got a bit ripped up on the Nurburgring this year.

Looking forward to those pix.

Will86 wrote:Its at a friends at the moment, I'll stick some more pictures up when its back.

To me, the original rear tire basically felt thin, if you turned in quickly it felt a little bit like you were dropping the bike. Completely fine on the roads, as I don't really do that, just a bit worrying on the track. I think it now has a bt90 on the rear, I'll check that when I pick it up. The wider rear makes it feel like the rear is dropping less suddenly as you lean it over, if that makes sense...? I'm happy with it anyway (got my knee down for the first time on it on another trip to Mallory since doing it) so it can't be too bad.

I did have a bit of a think about doing the front wheel, but I quite like how easy it is to change direction with the little front wheel (16"). Having read about it a little, it sounded like it would be best to change the whole front end, which I don't really want to spend the money on (Ignoring that I have pretty much done this on the back).

That feeling will probably just be a combination of narrow tyres and the 16/18 inch combination with the geometry of the nc24.

if you were already running a bt90 on the back what are you running on the front? don't mix radials and bias tyres.. I don't think you can get any radials in stock size so that will give you some weird problems.

the biggest let-down of the nc24 is in terms of track ability when compared to say an NC30/35... often you can pick up the nc24 for pennies but even trying to get it into a similar spec to the nc30 will cost you more than buying an nc30

the front brakes are much weaker.. tyre choice is not good, shock optnions are not good and front forks are not good either.

even with generic bt45s on a dry day you ll outrun the brakes and suspension before the tyres, just make sure your not mixing construction types.. will give you some weird feelings and can be unsafe. I had to replace the footpegs on my nc24 as I wore half of it away during spirited riding.. very easy to scrape as they are quite low and the bike is easy to turn.

it all depends on where / how you are riding and your own ability.. if its just a weekend toy or something you want to be comptetive in etc.

if your just beginning trackdays I would even waste any money doing "mods" until you have some riding experiences.. the 400 might get old quick as happens to a lot of people.. might need money for repairs after some offs, might decide a different 400 is going to be better in the long run.

some people get hung up on thinking newer tyres / shocks etc will make them faster when that isn't always the case.

when tracking a 30 year old bike best thing to check first is all the bushes and bearings are ok, they will give you weird feelings.. also biggest let-down on the 24 would be the shock and forks then the brakes so they would be first points of upgrades.. as well as not mixing tyre types, no point doing upgrades to mask problems.

so long as nothing is leaking and / or wornout like bushes / bearings you can still have a lot of fun and be quite quick on an nc24 in stock trim, one of mine is untouched running bt45s now I belive, just in terms of competivie racing against other 400s your going to loose out rider skill being equal due to the ability to brake later etc of the other bikes.