Wheels / Tyres moving from 14" to 13" wheels

[terrier1102]

I am sure this has been discussed before but still would be glad of your advice.

Seven SV  2002

Currently on Yokohama A021 185/60 R14 , there seems to be a dearth of replacement tyres on 14"

Therefore I am thinking to buy some 13" wheels for track days and road use can you please advise how to proceed on the necessary tyre size and to keep the same ride height, I am not necessarily looking for more grip

Gavin

[martyn]

If you switch to Avon ZZS 185/55/13 (without adjusting suspension) You'll lose 22mm of ride height.

Avon CR500 175/55/13 will loose you  27.5mm of ride height.

The closest you'll get is if you can find a tyre in 185/65/13. That'll be a 3.5mm drop.  All above without adjusting suspension of course.

Personally, I'd choose the tyre I want then adjust the suspension to my desired ride height.  No compromises that way.

[Agrippa]

I've just gone through this and went for Avon ZZS.  You can maintain the ride height at the rear using 215/55 R13 on an 8J rim. This also keeps the speedo accurate. The ride height at the front will have to be adjusted whatever you do. You will need adjustable spring platforms to get the set up right. It's a good idea to get the car set up properly at a specialist after changing wheels / tyres. Ride height, camber, castor, bump steer will all need correcting to get the best out of the car on track. You might also want to change the anti roll bar, and dampers.............got your cheque book ready ?

Adrian.

[Brian Deacon]

Hi. Ues this website for its size calculations. Works really well.

http://www.willtheyfit.com/

 

[JosephClarke]

My car has had the wheels changed from the original 14" minilights to Caterhams newer 13" wheels before i brought it, (I still have the 14" wheels as well)

I don't know if the owner swapped them or a garage, do I need to have the alignment etc redone and how do I tell if the speedo is going to be accurate? It seems to be based on roadside light-up speed signs :D

[lincslotus7.club]

 

For the wheels try Compomotive CXR from Simon @ Meteor Motorsport.

Good advice as he uses a Seven in competition & great service - my wheels came in a couple of days, the quality looks spot on so much better than the OE ones on my 2012 car!

[Dartmoor7]

 

Camskill have Toyo R888 in 205/60x13, you lose less than a millimetre in ride height.

[Mrp]

I have the CXR from Simon they are certainly a better quality than the standard wheels

Look nice as well.

Mrp

[JosephClarke]

Hi just a bit more detail on the set up of my car, advice appreciated,

The car had Caterham minilight wheels with Avon CR322 Tires all round in 185/70R13 from new.

The last owner changed this to the Caterham wheels as per here (I'm pretty certain these are the wheels)

http://caterhamparts.co.uk/product.php?id_product=26

These are running a brand new set of CR500's the rear wheels have 205/55/R13 and the fronts have 175/55R13

Looking through bill from the work, nothing looks to have been done to either the flat floor set up/alignment or the speedo after changing the wheels. Should I be looking to get both corrected?

Thanks

[martyn]

You can download a free GPS speedo app on a phone or use a satnav to get a GPS verified speed.  I wouldn't worry about it too much though. Speedos generally under-read by a margin.  Yours will just have a bigger margin as it has moved to smaller tyres.   You can see the difference is about 5mph at 80mph here: https://tiresize.com/comparison/  Depending on what speedo you have, you might be able to recalibrate it by flicking some switches on the back.

If you've never had a set-up/alignment then why are you worried now that it may be out?  You don't have a "correct" baseline to compare to.  Probably something worth doing in your ownership regardless of the fact that the tyres have changed.

[MereCat]

Had the same problem. Have a look at this link as I suspect this is what your experiencing.

took some off the dedion ears which fixed the problem for me. Went from 14 on a 97 to 13's

http://www.usa7s.net/vb/showthread.php?6123-Issues-with-13-quot-wheel-clearance-on-De-Dion-Caterham

[MereCat]

Speedo will be wrong due to change in wheel diameter. Sent mines off to Speedy cables http://www.speedycables.com/m.contactus.html

dont expect it back in a hurry though....

[MereCat]

*whistle*Always helps if you post in the right thread.....apologies all 

[JosephClarke]

Thanks will check the speedo itself it's a early 2000's Caterham branded one, regarding alignment I do plan to have it all checked anyway but was more concerned if I should get it done as soon as possible if it was likely it may have unbalanced the car etc.

Does anyone know of any Caterham friendly garages that could do the flat floor set up/alignment in the Norfolk / Suffolk area?

Thanks

[martyn]

I'd would not be any more concerned after finding out the wheels had been changed. Because how do you know the previous owner ever had it set up at all?  In any case it would have been set up for them and not for you.  There are no right or wrong setups (within reason), if the car drives how you want it to then you dont need to do anything.  If the car has behaviors you dont like then take it in to a specialist and get the setup modified.

For reference the change of tyres has resulted in the ride heights changing by -1.3 inches at the front and -0.65 inches at the rear.  Sump clearance for a road car is normally in the range of 2.5 - 3.5 inches.  I find it hard to believe the previous owner could reasonably accommodate at 1.3 inch drop without adjusting the suspension heights.  Assuming of course you have adjustable platforms on your car?

What is your sump clearance at the moment?

[JosephClarke]

I will measure it and check thanks,

[JosephClarke]

Measured, currently sitting at 2.2", so assuming something must have been done?

Ta