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Thanks Bram, but don't worry - I've already ordered some that are similar size to the proper wheels, I'm just undecided whether or not it'll look right with the body I have in mind. If it looks horrible, I'll then investigate getting something between the originals & 2.2s & mod the gearbox

Okay cool! But if you change your mind, i found them in my attic. Shape is bit worse then i thought but their oke.


Cheers, Bram

Just out of curiousity... how much smaller are these rims then compared to 2.2s for them to create gearbox issues?

For that matter (getting more curious) - would increasing the diameter of the wheels by, let's say, 15% be exactly the same as using a pinion that's relatively just as much bigger? Or a smaller spur of course...
Been thinking about that (and any consequence I may have overlooked) for my DF-01s that all have bigger wheels fitted.

It's like this - yes, loads of people stick big wheels on their standard geared cars & don't worry about it. Me on the other hand, I have an annoying requirement for things to be "right" or they play on my mind, increasing my insanity...

ThunderWotsit wheels are 50mm diameter, about 80mm overall diameter over the spikes.
Manual says in standard trim use 15T pinion. The motor plate caters for 13T-17T.
This car is fitted with 14T, I guess to cater for the slightly larger (85mm max O/D) Hotshot wheels that had been fitted to it. I've never run the car with the Hotshot wheels & 14T pinion, so my next statement is only a guess based on the assumption that what was fitted worked ok - from this, -1T pinion = +5mm wheel O/D, so a 13T pinion would work with 90mm O/D tyres. Of course, this could be rubbish....

As for percentage difference wheels verses pinions, I don't know, well not without doing the sums anyway, but I'd suspect that wouldn't apply cos there's more than 1 stage in the reduction ratio - yes the gear ratio is a fixed statement (eg 4:1 reduction) BUT because there's more than one stage to getting to that answer, changing one small part of it (ie the pinion) won't change the overall ratio by the same amount as the pinion-to-spur change.

Normally I'd work it out by picking a theoretical motor rpm, do the ratio sums for each stage of the gearbox, through to the wheels, to get a "road speed" number. Then, using this road speed, the assumed motor rpm, & the circumference of bigger/smaller wheels, work back through the gearbox to give me an answer for number of teeth on the pinion to do the same job.

If the wheel size isn't hugely different, you can normally get away with guessing, ie you probably won't notice the difference 1 tooth makes, 3 teeth different makes a big difference, but this is relative to the starting size of the pinion & type of car/wheels. For example, a Blackfoot is a bodge-up big-wheel car based on a standard buggy. The "Bodge" is the unsensibly small pinion. Small pinions on large spurs means greater stress-per-tooth, hence they strip gears. Going 3 teeth smaller on the pinion to fit bigger wheels just aint gonna happen, mainly because 7T pinions aren't readily available, (& would be a dumb idea if they were) but also because of the increased fragility this would impart to that part of the gear train. Going the other way (bigger pinion, smaller wheels) would improve the reliability.

The other possibility (Like Edou said) is change the spur. Fitting a smaller spur is the same as fitting a bigger pinion, is the same as fitting bigger wheels, ie you decrease the ratio ("Gear it up") eg 4:1 (4 turns of motor = 1 turn of wheels) becomes 3:1 etc. So, for bigger wheels, we'd need a bigger spur. All very well, but in a lot of cases, this isn't a good idea. For 1, with cars like the 'shot, you can't easily change the spur because it's also part of another gear, other cars just don't have the space to do it.

As I said, when my standard size wheels turn up, I can fit them & run the car, which should give me a better idea of what I can get away with before serious modification ensues. Of course, if it looks right & goes ok with those wheels, I'll call it finished

1st (Posh) Thunder Dragon is up on Ebay now, UK only though

Some wheels turned up today, good condition Mardave spike tyres, Schumacher dish wheels, 12mm hex fitting. Bit annoyed about it - even after a flurry of messages to/from the seller checking dimensions to see if they'd fit the Hotshot wheels (Which I was assured they would) turns out they're 5mm bigger I/D than he said, & don't fit. Don't like dish wheels, but I suppose I'm gonna have to use them. On the up-side, the O/D & width seems to look ok with the body. I've ordered some hex adaptors - 3 quid isn't enough to make me go out into the cold shed & make some! Toying with the idea of popping some holes in the dish wheels to make them look better, dunno yet though

Yes, Wild Oneish wheels would be good.
Could it be the tyres were stretched over the rim?
Hard to make up for 5mm though...

Yes I suppose it's possible they've been stretched a bit, but I removed them from the rims & they haven't returned to a smaller size. To me that suggests the seller was guessing & never actually measured them despite telling me he had.

Had a bit of a loose measure & line-up to get some idea of what to do about body mounts. Might do those tomorrow if the outdoors is a bit more inviting

Just twigged - you changed your avatar! NICE!

Yep, indeed I did. Kept Lars busy with that tonight.
The one of the C11 was pretty cool but that was taken as I got the car. And I don't have that shell anymore...
This car got sold as well but it has more of a "signature" (mine) on it.

I (we) found out about the avatars that the system will also accept gif images.
They look a bit tidier than jpeg when resized to 200x200 pix.
Just too bad animated gifs won't work 'cause I had a nice one in mind...