tennman117

Replaced my run flat tires with new Michelin pilot sport 3+ tires in 245x45x18 size.

I have a space saver spare size 145x70x17 which was sized for the original 245x40x18 tires.

the original diameter difference on the space saver was -2.8%
with the larger size tires the difference is now -6.3%

My question is how much difference is too much?
Searched the web but could not find any answer.

digitatc

I wouldn't worry too much about it, it's just a spare to get you to the shop and get the main tire fixed.

I don't even have a spare tire in my car. I have a air pump and quick patch kit. If my tire blows, I'll call the tow truck.

tennman117

I guess my main concern is if a blowout happened on the interstate and I had to drive several miles on the space saver to get to a tire shop.
Would the difference in diameter have any effect on drive train?

We are doing a trip to Florida later this month hence the reason for my question.

joemg

I picked up one of these at walmart for $25 and keep it in the trunk:
https://shop.slime.com/collections/f...nt=47564951496


I figured between that or my AAA membership, if I get a flat I have some options.

tennman117

Yes, those are good but unfortunately Michelin will void the tire warranty if it is used.
Also, will that damage our TPMS sensors?

joemg

I don't think I have any sort of tire warranty. I just recently took ownership of this car, but good to know for others/the future.

It says "tire sensor safe" on it.

DJWLDW

I would look at ordering the spare tire conversion install kit. Replace the run flats and call it good. I have installed 2 of them and BGW70 has installed 2 spare tire conversion kits as well. Unless you really really need the trunk space than the conversion install kit is the way to go.

Dennis

tennman117

I have replaced the run flats with Michelin Pilot Sport 3+
I also have the Lexus space saver spare tire.
The new tires are the larger 245x45x18 vs the stock 245x40x18.
My original question is if the stock Lexus space saver spare that is sized for the stock size tire would be too small for my new larger sized tires.

DJWLDW

tennman117

My son is running the 245/45R/18's on his 05 SC and has the spare tire kit and I will be installing 245/45R/18's come spring and also have the spare tire conversion kit in my 06 and do not think the spare size will be a problem. If things run normal now that I have installed the spare tire conversion kits in both of our SC's we will never have a flat tire again.

Dennis

Raven01750

Can anyone take a pic of an installed kit? I was just curious if any space is left in the trunk area after its installation. Thanks.

P.S. I should have done a search first before my request but didn't. If anyone can point me to a link I would be greatful. Thanks.

Paul

Bgw70

here is the thread with my two installations. The first used all replacement parts, the second I used some replacement parts, the other parts were modified to save money.

https://www.clublexus.com/forums/sc4...th-photos.html

DJWLDW

BGW70

Let me ask you a question. Have you had a flat tire since installing the spare tire conversion kits?

Dennis

DJWLDW

I followed BGW70's example for his 2nd spare tire conversion kit installation and modified a couple parts on both installations to save money and they both came out looking great

Dennis

Bgw70

no flats...but I haven’t had a flat since I was 19 years old. Couldn’t afford good tires back in those days.

Harold57

I have but none of the flats required the spare. They were slow leaks (nail in one and a leaky wheel in the other). I installed my kit at least 10 years ago.