Plz help me choose tyre sizes for GA65

[Stefan]

I need to choose some tyres to go on my GA65, which will be powered by a 1G with a lot of curry. Before I choose make/model, I need to settle on what sizes to get...

• Stock tyre size is 185/70/14, which means I'm allowed up to 235s under NCOP.
• My wheels are 16"x7.5".
• I'm concerned about traction with tyres that aren't wide enough.
• I'm concerned about wet traction with tyres that are too wide(this is Tassie, after all).
• There isn't a lot of clearance at the front when I test fitted them with the 205/55/16s that the wheels came with. Around 5-7mm between sidewall and coilover spring seats.
• Rear clearance isn't an issue
• I don't want to use spacers as this has to be engineerable.

Would 205s (often the minimum allowed on 7.5") all round in the right tyres and susp settings be adequate, or should I go wider tyres at the back? Would 215s or 225s give appreciably more grip?

Some sizes with their difference in overall diameter for comparison:
185/70-14 (stock)
205/50-16 -0.5%
205/55-16 +2.8%
215/50-16 +1.1%
215/45-16 -2.4%
225/45-16 -0.9%
225/50-16 +2.7%

Any thoughts appreciated!

[Norbie]

You probably won't be able to go much bigger than 205 on the front without modifying the guards, but IMO you should go as large as possible on the back. The trailing-arm IRS makes traction difficult with a high-powered engine; even with 255's on my MA61 I still struggle to get the power down. With 205's you'll just have a crazy wheelspin machine.

[IN 05 NT]

id go for some nice 225/50/16's...they will cope with a standard 1g. plus they are relatively cheap due to being a common size.

edit: i was running OLD 225/50/16 dunlops under the celica when it was making 195rwkw, was a lil sketchy in 1st..... (but a fresh set of nice NEW tyres would have kept it straighter )

[Stefan]

You probably won't be able to go much bigger than 205 on the front without modifying the guards, but IMO you should go as large as possible on the back. The trailing-arm IRS makes traction difficult with a high-powered engine; even with 255's on my MA61 I still struggle to get the power down. With 205's you'll just have a crazy wheelspin machine.

Guards are currently rolled somewhat with a hammer, and are going to be rolled properly, but clearance that way isn't such an issue - it's the spring seats which are robbing me of inwards clearance. Wheels were bought to clear brakes - +22 P1s at front with -8 from brake upgrade = effective offset of +14. Shame, becasue JCMO has exactly the same wheels & brakes at the front of his GA61, but with +32s, and still manages to run 225s.

I'm hesitant to have the front/rear sizes too different - what size fronts do you have?

[Stefan]

id go for some nice 225/50/16's...they will cope with a standard 1g. plus they are relatively cheap due to being a common size.

edit: i was running OLD 225/50/16 dunlops under the celica when it was making 195rwkw, was a lil sketchy in 1st..... (but a fresh set of nice NEW tyres would have kept it straighter )

Hmm... 1G is not standard at all though:

[IN 05 NT]

you'll spin a bearing b4 you spin a tyre

[Stefan]

...

[o_man_ra23]

I think you have the wrong offset brew... sorry. My RA23 and RA40s have all had 215s happily under the front end with no clearance issues. Unfortunatly I think your stuck with 205s on the front, but you should go 225s or 235s on the rear. Also, a larger diameter at the rear, combined with appropriate speedo adjustment will help to get traction down, as the tyre will want to squat a bit more.

[IN 05 NT]

235 will be fucking exp! as they are only made for jags....

[IN 05 NT]

235 will be fucking exp! as they are only made for jags....

[wilbo666]

it's the spring seats which are robbing me of inwards clearance. Wheels were bought to clear brakes - +22 P1s at front with -8 from brake upgrade = effective offset of +14. Shame, becasue JCMO has exactly the same wheels & brakes at the front of his GA61, but with +32s, and still manages to run 225s.

I'm confused, JCMO has more positive offset which means his wheels sit in further that yours...

i.e. JCMO should have the problem worse than you!

Cheers
Wilbo

[Stefan]

No-one read the bit about my coilover spring seats are robbing me of clearance. They happen to be in line with the tyre sidewalls. Shorter springs might help, but I'm not that the collar is long enough.

JCMO has stock struts.

[Stefan]

For reference, this is how the +12s sit with 205/55s. The +22s with -8mm upgrade will sit 2mm further in.

[o_man_ra23]

Coilover spring seats are normally narrower than regular spring seats arent they??

[Stefan]

Yes, but like i said they happen to be in line with the tyre sidewalls.