[rks]

For my experience with upgrading to 5" alloy wheels from the stock 4" steel wheels, see the T-BHP thread "Upgrading wheels/tyres on Santro". In my case the alloys were a perfect match in terms of PCD and bore diameter, but the offset for my alloys is +26 mm, as compared to the stock +46 mm. But overall the pickup and handling (including high-speed cornering) of the car has markedly improved at least for speeds up to 120 kmph. For higher speeds the handling remains about the same.

I expect an increase in fuel economy for city driving because I need to do less frequent gear changes due to noticeably increased pick-up. E.g I do not need to shift to first now unless the car slows down below 5 kmph, whereas earlier it was 10 kmph. Similarly I can keep the car in 3rd/4th at ~20/30 kmph, whereas earlier it was ~30/40 kmph, etc. The fact that the alloys are lighter plays a very important role here -- with 5" steel wheels, I am sure I would have lost out due to the increased weight.

[elf]

rks, what's the size of your OE tyres, & what size have you now installed?

[Vid6639]

elfie, OE tyres are 155/70-13 on 4J. He has the same OE tyres on 4.5J.

http://www.team-bhp.com/forum/tyre-a...tml#post386150

Here for lots more info go through this.

[elf]

Thanks vid6639. By any rule of thumb, that shouldn't result in increased acceleration, unless his earlier tyres were completely bald / hardened / had no grip & as a result, he was simply standing still spinning his wheels every time he accelerated.

I thought that maybe he'd lowered the profile of his tyres, which would definitely aid acceleration, but drop top speed & result in a speedo error.

rks: Dude. How?

[kpzen]

Originally Posted by elf

rks: Dude. How?

Here it is explained extensively by rks....

http://www.team-bhp.com/forum/tyre-a...tml#post386150

[rks]

Originally Posted by elf

rks, what's the size of your OE tyres, & what size have you now installed?

As pointed out by kpzen, I have explained this in another thread. With the *same* stock 155/70 R13 S322 tyres on 5J X 13" alloys (as opposed to 4J X 13" steel wheels earlier), you get a wider contact patch, and hence better grip. Secondly, the handling improves (especially cornering) because now there is very little sidewall flex -- I can see the sidewalls more or less straight with alloys, whereas they were flexed with my 4J steel wheels. This would make the ride a little harsher, but I feel that the wider 5J alloys handle potholes better than with steel wheels. With greater grip you get a noticeable improvement in pick-up, at least the first four gears, given that the alloys, despite being larger, are still lighter than the steel rims. But in fifth gear, the steel wheels seem to do better in terms of pick-up at higher speeds (>100 kmph?), including possibly a marginally better top speed, but I need to test this out a little more.

Edit: See also Samurai's experience in the same thread cited by kpzen. He gets improved pick-up with upsized tyres (165/65 R 13) and with 5J alloys. I feel his handling (especially cornering) at high speeds would not be as good as with 155/70 tyres on the same wheels, but he would get much greater ride comfort. So it is a compromise all the way.