Aspect Ratios- help the new guy out

[Jesse D]

Looking through the threads here I couldn't find a quick answer to my question so figure there is always room for one more on the basics. My Caterham came with two sets of wheels, 15" and 16". Currently has 195/45R15 Avon CR500s and 205/45R16 Goodyear Eagle F1s fitted. With the 15s fitted I have less than 3" clearance under the engine, and it has proved difficult for trailering and I suspect for driving Maine's back roads. I hope to do a little autocrossing/track driving so plan to use one set of wheels for "street" and one for "other". My question is specifically with how best to get a little better ride height for the street. I'll gain about an inch with the 16s right now but I'm wondering if the way to go is to fit a higher profile tire to the 15s for street use and keep a lower profile on the 16s or the reverse. Comfort vs. handling is the other question. What say the experienced folks here?

 

FWIW, I like the look of the 15s better, today at least.

[yellowss7]

Any chance you have adjustable spring perches? That allows you to raise or lower the height and also corner weight the car properly.

[Taber10]

I'm thinking the "silver" five spoke are "16s" and the blacked out ten spoke are the "15s" but I don't really know. The five spoke are "traditional" and were fitted to many Caterhams: They "look" like street wheels, and complement the looks of a great looking traditional Cat. The ten spoke look more "aggressive" and could be thought of as "track" wheels for your other driving. With NO other "black-out" parts, except the windscreen mounted rear view mirrors, the black wheels don't really complement the traditional looks of the Cat. I think they would be more suited--appearance wise--to the track use. But, as I don't "track/autocross/etc." my car, I really don't know past the appearance. Just my opinion....

[coffee break]

Something to think about is tire availability. Which rim dia and width have more auto-x and track compounds to choose from.

 

BTW You have the same color scheme as my 7, classic.

[MudHut]

http://www.rimsntires.com/specspro.jsp

Take a minute and play with this tire size calculator. It's an excellent visual aid for getting to know the differences in sizes and how they compare. Try a 205/45/15 and compare to the wheels and tires you currently have mounted.

 

On edit, knowing the width of your current wheels will help with fitting the tires you are looking for.

 

Jay

Edited December 3, 2015 by MudHut

[Kitcat]

I think a 16" wheel is going to put you 1/2" higher than a 15" wheel, not 1", assuming all other variables are equal.

[super7guy]

The best ride is going to be with 13" rims. The classic sizes of 165, 175 or 185-13 are available from some manufacturers and from Coker. The rims are also among the cheapest.

 

Wayne

[Sean]

Going from a 205/45-16 to a 195/45-15 results in a 17.2mm (0.68") lower car.

Going from a 205/45-16 to a 205/60-13 would result in a 7.35mm (0.29") lower car.

[Jesse D]

My apologies to the group for starting a thread and not keeping up. In sort of order . . . .

1. I don't know if I have adjustable spring perches- were they a standard Caterham feature in 1993?

2. After a summer's use, it turns out ride height was never a problem with the 15 inch wheels (which are the dark ones), and the beavertail I had put in the trailer I bought means no difficulty in driving the car right in- the race ramps I thought I needed weren't needed. The one inch measurement was done by just laying a measure across my existing tires, I forgot that only half of that improves the ride height, Sean's numbers are right, thanks.:-(

3. Most importantly the car is perfectly comfortable driving, even after I put in fiberglass seats with no cushions to lower my head height a little and allow for proper harnesses- this is a pleasant surprise.

4. I just don't like the look of the 16" Caterham silver wheels. I'm headed in the direction of keeping the 15s with the Avons for autocrossing and the little track use that I might do, and getting something in the minilite style for street use- maybe 14's there with a higher profile tire. I just don't like the big rim look, though I'm not sure about 13's.

 

My autocrossing skills could be classed as beginner but with some skill developed over the years. It is clear the car is much better than I am as my times are not too far off the best times posted (this is local Maine autocrossing, pretty low key. The Avons seemed great for this purpose, given what I know. I also know I won't be driving in the rain unless caught (I'm usually without the top) and my street driving will not be that dramatic either- autocrossing is the fun place to find the limits rather than the street for me- I must be old.

[Croc]

Jesse - Do they still run the autocross on the sloping parking lot on Commercial Street/Center Street in downtown Portland? Or have they found somewhere more spacious to run it? I have memories of sharing a Miata for a day auto crossing on that parking lot in 1997 when I used to live in Portland.

[Jesse D]

No Mike, they haven't run that one in a while. I probably watched you that day, it is one of the things that drove me to my Seven- it looked like so much fun. Currently we run at an overflow lot at the airport, a local BMW dealer and a couple of LL Bean parking lots up in Freeport. Bigger lots, but locations where no one can easily see us, which I think is a shame. Simple local autocross is really easy to do and I think if more people saw it, they would try it. Being Maine, a few people run pickups- would you believe a properly set up Chevy midsize has great front rear weight distribution, according to the owner, who does pretty well.