Wheelbase track width discrepancy between front and rear

[s70mev]

Ok, so recently I managed to get my project rolling which is a great help as I can now relocate it out of the marquee to a workshop that I'm going to rent to save the woes of the winter. Having put all four wheels on, I can't help but notice that the distance between the two front wheels is greater than the distance between the two rear wheels. Is this normal? I am aware that my rear wheels need spacing to bring them away from the wishbones - the clearance is much too close, and possibly even touching when suspension is in full droop. I acquired 4 24mm wheel spacers to solve the clearance issue, but I purchased these before I realised that there was a width discrepancy between the two front wheels and the two back wheels. Is it going to be necessary to space the front wheels with narrower spacers to make the front and the back match up? I'm presuming yes!

[martinw]

Front and rear track on the Sonic is pretty much the same. The "standard" suggested approach is ET40 wheels on the front, and ET15 wheels on the rear, with 25mm spacers on the rear. That's what I've got on mine, and everything fits nicely. You shouldn't need any spacers on the front; even with the alternative approach of having ET40 wheels all round, with 50mm spacers on the back, you still don't need front spacers.

The Sonic does have a very wide track for such a relatively small car; there's no need to make it wider still!

Martin

[airforceone]

I made a similar comment to Andy about his Sonic a few weeks ago.

I had my rocket parked behind his and you can see that the track is quite a bit wider.

I believe he has 50mm spacers on the back.

[andybaird]

Hi s70mev

airforceone is correct. I have 50mm spacers on the back. I also have extensions on the steering rack that make the front wider than the back. I will take some measurements the at the weekend when I have it at Donnington.

Cheers
Andy

[s70mev]

Cheers chaps. I've got rack extenders on the front as the design of the wishbones makes it necessary. 50mm spacing... that's a hell of a lot of spacing! It makes my set of 4 24mm spacers redundant. damn!

[welshmarks7]

Hi guys, sorry to jump on the band wagon, I too have a difference , it is 35mm narrower on the rear track using the et15 rear wheel with 25mm spacers and et40 wheels on the front. Would this need to be rectified (I could fit 2 x 16mm spacers in addition or 40 mm spacers leaving a difference of about 6mm) has anybody had this issue?
Mark

[davef]

Hi guys I spoke to Paul at RTR about this his advice is ET40 (ford) offset on the front and ET15 ( Peugeot ) on the back no spacers needed? At least I think it was that way around! Def no spacers needed with the right offset though

[martinw]

davef - I just checked the build guide, and it definitely says:

<<.....with a 40mm (FORD) offset wheel to the front and 15mm offset (PEUGEOT) to the rear with a 25mm spacer (or 40mm offset wheel with 50mm spacers).>>

I don't think this is something that will have changed since RTR took over manufacturing (....my Sonic was from MEV), but I may be wrong. Without a spacer on the rear of mine, with an ET15 wheel, there would be insufficient room to fit the wings / wing supports without them hitting the bodywork during suspension movement. I'd check out the advice from RTR.....I don't think there is a viable "no spacer" solution for the Sonic. And if you want identical wheels all round (ET40) you have to go to 50mm spacers on the rear.

Martin

[mawdo81]

What size track rod extensions have people used please? I'm using the RTR Steel Uprights with Focus Track rod ends and have huge toe in with no extensions and huge toe out with...

[Stiggy]

We used to supply 2 threaded bars (12mm) and 2 threaded sleeves, all 50mm long. The track rod screwed in one end of the sleeve and half the threaded bar in the other end. The other half of the threaded bar screwed into the rod end.

[mawdo81]

Thanks Stiggy, was that 50mm per side, or 50mm total? If preside is there any issue with unequal tie rod lengths?

[Stiggy]

each side, 2 of each but if yours are too long you may have to cut the ends of your track rods, maybe the wishbone length was changed, ask Angus.

[equilibrium]

I can't comment on what RTR were supplying with the steel uprights and Focus track rod ends, but we are using the wishbone jigs supplied by Stiggy, aluminium uprights and RS 2000 track rod ends. With this setup we are using 50mm (per side) steering rack extensions.

[daydreamer]

I have four ford ET40 offset wheels , no spacers at the front, 50mm spacers at the rear.

I believe the logic is like this;

The front wheel track is pushed out by long wishbones, that is why there is are 50mm extensions to the track rod ends on the steering rack and no spacers on the hub.

The rear track is dictated by the donor vehicle drive shafts. So the extra 50mm is achieved by adding spacers to the rear hubs. Putting the 50mm spacers on the rear hubs surfaces, where the wheels are attached, means that the front and rear hubs are then the same width and can take the same wheels.

50mm spacers are considered large and not everybody approves. personally I think if they are well made, hubcentric and bolted on then they are ok. I'd agree than non-hubcentric , bolt thru spacer plates ( those that are loose when the wheel is removed ) probably reach their limit at a few mm. I imagine the recommendation for rear wheels of an ET15 or ET20 design is put forward to avoid any controversy around large spacers.

[kiwicanfly]

I am curious why the Sonic design is different to the Rocket in this respect, I was under the impression they shared common design but the Rocket uses 35 to 40mm offset (varies who you speak to) and no extensions on the rack.

What is the purpose of the wider wheelbase?