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Old 27th August 2010, 10:58   #16
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Default So what tyre pressure on an upsized/downsized tyre?

Nice article on C&D, thanks GTO. My Fabia comes with 14" alloys and I was considering an upgrade to 15" (like the ones Skoda ships out in Europe)

What I'm not sure about though is what pressure to maintain on a tyre/wheel combination that has been upsized/downsized. Does it go up or down with an upsize?

Any thoughts?
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Old 27th August 2010, 12:11   #17
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Quote:
Originally Posted by Vibhanshu View Post
For a car like swift, is 195/60-15" an overdo? (company says 185/70-14")

I think even the width of the Rim makes a difference. A lil narrower rim might give that extra ride quality as the tires might bulge outside. Huyndai usually goes this way.
Yes, the rims specs and suspension geometry also makes a difference.
Quote:
Originally Posted by lionell View Post
This is a brilliant thread GTO. I was looking out to post a few questions on tyre upsize for the Aveo UVA. Currently it holds a 155-80-R13. I wanted to upsize to a 15" alloy, is it a good bet or should I stick to the 14" ones.

What's the best tyre size then?
185/60-14 is the best upsize for UVA. The LT version comes with that size.
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Old 27th August 2010, 15:19   #18
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Quote:
Originally Posted by GTO View Post
Remember my thread (Why do cars with low profile tyres tramline more?) on why cars with low profile tyres tramline a lot more?

Summary: Upsize, but don't overdo it. Large (heavier) wheels, super low profile tyres and an ultra-fat contact patch can actually kill performance. Choose a reasonable upsize instead.
Great thread GTO! Can I add a few more to the list:

1. The tyres SLR (Static Loaded Radius) are also quite significant in selecting tyres. A upgrade that is closer to the current SLR dimension is always wise.

In layman's term, the SLR determines the current Ground Clearance, replacing with a bigger rim but a lesser SLR will directly result in lower Ground Clearance. Also, choosing a tyre with higher SLR will increase the ground clearance but will impact the vehicle clearances i.e. wheel bump conditions, steering lock to lock with the underbody, etc.

2. The tyre aspect ratio is also an important factor in determining the overall ride quality. Thick tyres behave poorly in handling parameters. Lower ratios result in better ride, e.g. 155/75 is better than 155/80. But do not over do this as very small aspect ratios result in higher grip rates that actually lowers your FE.

The OEMs consider these aspects as well while developing the product. However, they choose the tyre that is a trade-off between FE, grip, ride quality & life. It is the responsibility of the customer to choose his tyre upgrades wisely, based on his personal priorities.


Quote:
Originally Posted by blackasta View Post
The best upgrade from 155/80R13 is 185/60R14 or 195/50R15.
I would say stick to 14".
Its the same tire profile I upgraded from/to.
Agree with you!

Like to add a little more to clarify the upgrade.

Technically the 50 series has only one rim size of 16" (Believe it is a typo error). the size might be 195/50R16 or 195/60R15. Assuming it is the latter as R16 is beyound your scope of upgrade.

155/80 R13 has an SLR of 262mm. The option 185/60R14 has SLR 265 & 195/60R15 has SLR 282. Suggest upgrade to 185/60 R14, it is better for you.
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Old 28th August 2010, 11:40   #19
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thread came it at such perfect timing!
i have a aug09 swift vdi, done 44k kms and due for a tyre change. the car is a daily driver over broken city roads, and also travels a lot in and around the state.
having put 13" wheels on the alto, i wanted to upsize the swift to 16s. My hunt for 16s ended in disappointment as my regular car accessory shop did not have too much variety. This was inspite of everyone reccommending a max of 15 inchers for the car, but i wanted 16s for the not-stock-but-not-OTT look.
came back, read this thread.
thought of all that could happen with the car on 16s if i went high speed through a bad patch, over a big pothole or even prolonged use on far-from-perfect roads that the car regularly sees.
then again, suspension wear on the car, increased body rattle on an already poorly built car, the constant thought that the-car-cannot-be-used-on-that-road finally made me a bit wiser.
the car plays workhorse most of the time, and when i do want to have a little bit of fun, she does not disappoint. so it was more of a head-over-heart decision.
finally settled down to 205/60R14 Yokohama ES100s about 2 days back.
The smile is now wider. I feel safer. And no wrinkles on the forehead anymore!
Sometimes, the Boy in us HAS to take the Back Seat.
Thank You GTO for the wonderful thread.

Last edited by satya180 : 28th August 2010 at 11:41. Reason: Grammar!
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Old 28th August 2010, 16:30   #20
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Thank you for this, GTO.

I've got 195/60 R15s in my Ikon and my Swift (S-drives and A-drives respectively). They're both upsizes, but I don't consider them OTT. I find the handling is significantly improved - I have much more confidence in the handling of both cars, but on the other hand I feel that the Ikon is marginally down on acceleration and I've noticed that the wheel deflects a little bit on a bumpy road.

I was VERY tempted to get 205s in both, but common (and fiscal) sense prevailed and in hindsight I'm glad I didn't.
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Old 29th August 2010, 14:17   #21
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Lovely dedicated thread GTO! Such specific threads do a world of good. Like somebody just pointed out, knowledgeable people could perhaps draw up a chart from which people like us could benefit and not taken for a ride like the below:

Amongst the many "gyaan" one receives from friends and gurus (including reviews and personnels alike), there is always a thought which pops up right after the installation. Same's happened with me. Unfortunately I did not have the know-how of Team-Bhp back then and I had upgraded my tires for the Swift from stock 165/80/14 MRF to 205/55/15 Falken. And that was for a simple reason - BLING! I did not have any information of the performance of that tire, the repercussions of such an action on the suspension, all I knew was it was a beauty! Now people, the Swifty's run 10k (5k with the upgraded tires), should I stick to it (probably risking more) or change ASAP to the more recommended (as read on Team-Bhp) 195/60/15.

Yours hopingly
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Old 29th August 2010, 17:31   #22
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I changed the stock tyres of my Elantra when I bought it in 2007. Though my knowledge about tires and alloys was very limited my decision was to agree to my friend who had a tire/alloy shop in BLR and he decided the size and tire. I think this thread makes a lot of sense to people like me who want to upgrade their wheels with limited knowledge. I think team-bhp is making a great effort to impart good information which is very useful to all.
Elantra came with 195/60/15 and I upgraded to 205/50/16. After nearly an year of upgrade through team bhp i came to know about the tire size converter and if the upsize is correct or wrong and how it really matters to the performance of the car.
Currently the tire size converter says that my upsize is well within the limits. I have gained a lot of grip and the car really responds to my wish. The negatives being I have lost the comfort levels on the car and the suspension also has become weak due to a pothhole that was really wide and deep.
GTO's trip to Malaysia will make people gain some "required" knowledge.
This is required since most of the stock tires are not up to the mark and upgrade really makes sense,
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Old 29th August 2010, 20:23   #23
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Good thread.I had replaced my vista's tyre to 185/65/r14 (kept the same wheel size) but in my Linea(as correctly GTO pointed out) i just changed the tyres to Michilline PrimaLc(from goodyear) with the same 195/65/r15 size because linea is having low GC and up sizing to 16' with a low profile didn't look like to work keeping in mind our road conditions.regards
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Old 29th August 2010, 21:55   #24
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I "changed" my OHC 1.5 's tires from stock to 175/65/15. Which I suppose is the stock tire size of the ANHC (?). I'm an enthusiastic driver although performance is not "all" I look for in the Bangalore traffic, so grip n high speed handling is not that important to me.

How different would it be, as far as the driving experience is concerned, say if I'd gone for 195 on the same 15inch rims?

Is it right to call my "change" an upgrade?

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Old 29th August 2010, 22:19   #25
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Very useful info on Upsize, Thanks GTO!

Agree with Jaggu, for wheels upsize, +1 is best, +2 the max.
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Old 30th August 2010, 17:39   #26
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Quote:
Originally Posted by GTO View Post
Remember my thread (Why do cars with low profile tyres tramline more?) on why cars with low profile tyres tramline a lot more?

At the Sepang track event (Driving a Formula Renault at the Michelin Pilot Experience, Sepang!), I asked someone from the Michelin Motorsports team why race cars don't wear super low profile tyres, while most after-market modified cars seem to sport 19 / 20 inch wheels with tiny sidewalls? Here's what he had to say:
  • The larger the wheel, the heavier the wheel + tyre combination. This increases unsprung weight, not a good thing
  • Super low profile tyres actually suffer from poorer grip on bumpier tracks. On an uneven surface, a taller sidewall can absorb bumps, where a low profile tyre would simply deflect. This, in a way, explains the tramlining that I was complaining about in the Vtec. Now, when hurtling down a bumpy Lonavla ghat section, which combination do you think will offer better grip? Which Indian road is perfectly paved again?
  • Generally, the larger the wheel size, the thicker the available tyre sizes (ever heard of a 195 mm tyre on 17 inch wheels?). Oversized tyres can actually SLOW the car's acceleration times
  • Some googling on the matter lead me to C&D's test article comparing different wheel & tyre combinations. Surprise surprise, 19 inch wheels with fatter tyres actually had lesser grip than 18s with thinner rubber. And there wasn't any difference in the skidpad rating of 225/45 R17 versus 205/55 R16 sizes! Note that the thinnest tyres recorded the best acceleration times
  • As is well known, the lower the profile of your tyres, the higher the rate of suspension wear & tear
Of course, a wheel upsize with lowered side profiles lead to sharper steering response and superior grip on flat roads. Within the Indian scenario, most OEM wheel + tyre sizes have smaller wheels + large sidewalls for ride comfort + costs (the smaller the wheel, the lesser its cost). Enthusiasts looking for a better driving experience should definitely upsize their wheels & tyres, but the point of this thread is....we probably shouldn't go overboard.

Most importantly, remember, its the quality of tyre that makes all the difference. A 205 patch high quality compound will inevitably offer you more grip than an average 225 patch tyre.

Summary: Upsize, but don't overdo it. Large (heavier) wheels, super low profile tyres and an ultra-fat contact patch can actually kill performance. Choose a reasonable upsize instead.

This is a very nice and informative piece of advice. We need to draw a line at a proper place. There is a very thin line between madness & intelligence.
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Old 1st September 2010, 14:43   #27
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Quote:
Originally Posted by rajess_in View Post
Great thread GTO! Can I add a few more to the list:

1. The tyres SLR (Static Loaded Radius) are also quite significant in selecting tyres. A upgrade that is closer to the current SLR dimension is always wise.

In layman's term, the SLR determines the current Ground Clearance, replacing with a bigger rim but a lesser SLR will directly result in lower Ground Clearance. Also, choosing a tyre with higher SLR will increase the ground clearance but will impact the vehicle clearances i.e. wheel bump conditions, steering lock to lock with the underbody, etc.
This is a great thread indeed .

Coming to SLR, @rajess_in, can you please update on how can we calculate the SLR? or is it mentioned on the tyre? Without Load the SLR will be tyre's outer radius. But when loaded this will be decrease.

SLR can be defined as - the radial distance between the road surface to the axle center under nominal tyre load /inflation conditions.

Is there some standard for defining this load? Again this load should vary from car to car and also depending on usage (number of people).

I used to apply one simpler formula to compare tyres. Just calculate the outer diameter of your current tyre and compare it to the outer diameter of tyre you are planning to upgrade. If both these are nearly equal it is a good conversion.

Quote:
Originally Posted by rajess_in View Post
2. The tyre aspect ratio is also an important factor in determining the overall ride quality. Thick tyres behave poorly in handling parameters. Lower ratios result in better ride, e.g. 155/75 is better than 155/80. But do not over do this as very small aspect ratios result in higher grip rates that actually lowers your FE.
IMHO tyres with lower Aspect Ratio are better in handling. For ride quality we need a higher aspect ratio on a tyre, i.e., the width of the tyre should be more for smooth ride.

Overall, the summary of the thread looks like - Dikhawe pe mat jao, apni akal lagao, meaning - Don't just go over looks, use your brain.

Last edited by gou : 1st September 2010 at 14:46.
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Old 1st September 2010, 17:59   #28
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Quote:
Originally Posted by gou View Post
I used to apply one simpler formula to compare tyres. Just calculate the outer diameter of your current tyre and compare it to the outer diameter of tyre you are planning to upgrade. If both these are nearly equal it is a good conversion.
+

Tire size calculator

Try the above link to check for all your tyre upgrades. This is very simple & easy to use.

Quote:
Originally Posted by gou View Post
IMHO tyres with lower Aspect Ratio are better in handling. For ride quality we need a higher aspect ratio on a tyre, i.e., the width of the tyre should be more for smooth ride.
Yes, you are right.
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Old 1st September 2010, 18:36   #29
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I Upsized my OHC from 175/70R13 [I think this is what the stock size is] to 205/50R15 & got stiffer suspension.

I do tramline quite a bit, but the added traction is worth it.

I upsized to 205/50 rather than 195/50 because they looked cooler & they were like some 4 - 5 hundred bucks more expensive than the 195's.
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Old 3rd September 2010, 07:31   #30
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Great Thread!

Cost cutting on some of the Indian cars are visible on their tyres. The standard tyres on swift (Vxi) is pretty narrow and can be a little dangerous considering the sweet handling characteristic. Quite a contrast really, make a car that begs you to push her around the corners and then equip her with Tyres that will most certainly kill you.

Upgraded mine to 195/60 R15 and the drive, braking is now much better. Some say that 205's would have been better, but anything over 200 for a cover with less than 100 horses is an overkill.
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