Does anyone know the weight of the stock 15" rims for the MC? I'd like to compare them to the Kosei K1 TS. The Kosei K1 TS is listed on the Tire Rack site as weighing 10.6 lbs for the rim only.

Thanks,

Joe

 

Which stock 15" rim do you have?

R81 7 hole 15x5.5" rims are 12 pounds each.


R82 8 spoke 15x5.5" rims are 15.2 pounds each


R93 5 spoke rocket 15x5.5" rims are 14.8 pounds each


The Kosei K1 TS is 15x7" and will work with the MC
For street use and comfort 205/55-15 is a wide tire available in many brands at a reasonable price.

 

I was thinking of the R81. If they are only 12 lbs, I might stick with them. What is the widest tire that can safely be installed on them? 195/60/15?


Thanks,

Joe

 

Joe,

The R81 is 15x5.5" so the widest tire that can easily fit would be 205/50-15 but the tire diameter is only 23.1" which is less (smaller) than the stock 175/65-15 tire which measures 24.4" in diameter.

Assuming stock MC suspension:

185/65-15 will fit. Tire diameter is 24.4"
195/60-15 will fit. Tire diameter is 24.2"
205/60-15 will fit. Tire diameter is 24.7"
205/65-15 will fit. Tire diameter is 24.7"

Another good choice is 205/55-15 which will fit the R81 rim and have a 23.9" tire diameter which is very close to stock.

On the extreme side it is possible for a very determined tire installer to mount a 225/50-15 tire on the R81 rim. The tire is meant for 6-8" rims. The tire diameter is 23.9" so it will work but weighs 2 pounds more than the 205/55-15 size.

 

Thanks for the reply. I think I'll probably go with a 195/60 or 205/60, depending on tire availability. Those seem wide enough for me. I was originally thinking about the Kosei K1 TS in 15" to reduce weight, but $600 for less than a 2 pound savings doesn't seem worth it.

 

Both these sizes are good for use with the stock 15x5.5" rim- it's a perfect fit for both.

Weights are:
195/60-15 about 18 pounds
205/60-15 about 20 pounds but varies with the tire selected.

60 series tires won't corner as well as 50 or 55 series tires but the ride will be smooth/comfortable and the performance for the street will be good.

Moving to Kosei K1 TS does loose a little weight 10.6 vs 12 pounds but you miss the reason why we switch- it's 15x7" vs 15x5.5". The extra 1.5" wider rim allows for use of very wide tires up to 225/45-15 with excellent results for cornering in autocross or on the track. For street use this is not useful because you can mount tires as wide as 205mm which is good enough.

 

I put a 205/60-15 on a stock R-82 rim for my 02 MCS and I'm glad I did it.

I will tell that I sacraficed a little in appearnce and probably even more in cornering capabilities but WOW! does it ride better. I was convinced with the 16" run-flats, that this MCS was going to turn into a rattle bucket. It did'nt roll-over bumps, it hit'em head-on.

And as far as cornering...It will still go thru a curve faster than I care to make it go.

YEA! I'm sticking with this tire/wheel combination for now.

 

Thanks for pointing that out. I forgot about the wider tires. I guess I might also get a little better cooling for the brakes with the K1 TS rims because of the larger openings, right? Will running those move me into a different class for autocrossing? I also forgot to mention that I plan to get the sport suspension plus instead of the stock suspension when I order. Will that affect clearance?

Thanks for all the info everyone. I'm really enjoying this forum and counting down the days (and pennies) until I can order my cooper.

Regards,

Joe

 

Joe,
A little better cooling isn't a bad thing but I'm not sure if the spoke design of the K1 TS will do the trick- it's possible. I do notice that some spoke designs that are more open attract less brake dust!

In H-stock class you have to use stock sized rims of 15x5.5" with close to stock wheel offset (+ or - 0.25" from stock offset) and any DOT approved tire.

The K1 TS is too wide at 15x7" to be used in stock class so you would have to move to Street Touring S (STS) for the MC which allows any wheel up to 7.5" width, tires up to and including 225mm with minimum tread wear rating of 140 (street tires such as the Falken Azenis Sport) and not the Pirelli PZero Corsa (excluded tire in 2005 rule book).

Next higher class would be F Street Prepared for the MC and that allows for any tire including R compounds, any wheel and wheel offset, spacers, wheel studs/nuts.

Sport suspension plus is good for autocross and will not affect tire clearance for your purposes. But the everyday ride is a little stiffer especially with runflat tires.

 

You may want to check tire rotations per mile to also watch for variations in tire sag due to the car weight. This will vary over a slight range and does not always correspond to whell diameter.

 

I'm not sure if I'm ready for that. I'm a strict newbie with a diaper rash, so I probably want to stay in the stock class while I'm learning.

Joe