[RoaringEngine]

wow!! thanks for the headsup ram. I didn't know about the "factor-of-safety". Then why worry? I will go for it and let you know how it goes :-)
*thanks*

[ThE_DoN]

OT : just saw potenza G3's for Maruti 800 in a shop... Excellent build quality
Cost 2050 per piece.

[Technocrat]

Originally Posted by SLK

I wonder .. if it was so simple to put a BIGGER tyre why don't manufacturers do it?
Better fuel economy?.. due to change in gear ratio?... theoritically yes. Then why don't manuacturers do it?
Better ride? ... yes..
better handling? .. yes (provided it was on 13" rims)

Then whats the down side? nothing?
No, there has to be something! maybe I can't think of it!
For one, increasing ride height is NOT good for handling.

Can someone tell me the downside?

Atleast in the case of M800 bigger tyres would also mean heavy steering & more load on engine. The change in gear ratio to get more fuel effeciency would mean sluggish engine. They give as a combination which is best suite for average drivers.

[adya33]

Originally Posted by Technocrat

Atleast in the case of M800 bigger tyres would also mean heavy steering & more load on engine. The change in gear ratio to get more fuel effeciency would mean sluggish engine. They give as a combination which is best suite for average drivers.

no techno, they might be doing it to protect Alto.
If 800 gives more FE, handles well, rides better then why would anyone go for Alto?

[Ram]

Originally Posted by Technocrat

At least in the case of M800 bigger tyres would also mean heavy steering & more load on engine.

Hey, we did not double the tire wall height or something. The increase in steering load and engine load, due to marginal increase in rolling radius is hardly discernible at all!

Originally Posted by Technocrat

The change in gear ratio to get more fuel efficiency would mean sluggish engine.

Again, how much marginal sluggishness can you measure here?

As far as speed is concerned, while, I never exceed a quiescent 100 km/h on the expressway, I once touched 130 km/h on the expressway with the the old 70% aspect ratio tires.. I did so on the new taller 80% tires too! In fact when it indicated 130 the actual speed was 137.4 km/h.

Yes the acceleration must be 5.7% sluggish, so the same acceleration is achieved at slightly higher rpm than before. No sweat!
But I can live with 5.7% weaker acceleration, particularly as I get 16 km/litre in the city and 29-something km/litre in 5th gear on the expressway at 90 km/h.

As adya33 points out, Maruti now uses my 800's taller tires, MPFI 12-valve engine and 5-speed gearbox, on their heavier Alto. The 2002 model 800's 5-speed 4-valve per cylinder 800, could blow the doors off the heavier Alto. That's why Maruti safeguarded the Alto’s existence by downgrading the 800 back to an older spec.

Originally Posted by Technocrat

They give as a combination which is best suited for average drivers.

Here are some cars for average drivers like myself

[Technocrat]

LOL Ram you kidding rite, those aint avg driver cars

May be I phrased it wrong, they make cars what commuters would like & not what a driver would

[humyum]

Originally Posted by ram

As adya33 points out, Maruti now uses my 800's taller tires, MPFI 12-valve engine and 5-speed gearbox, on their heavier Alto. The 2002 model 800's 5-speed 4-valve per cylinder 800, could blow the doors off the heavier Alto. That's why Maruti safeguarded the Alto’s existence by downgrading the 800 back to an older spec.

Dude are u kidding about the average part.29 something on the highway .I know its an mpfi 5 speed 800 but alto shares the engine with your 800 and weighs 100kgs more than your 800 but alto gives a mileage of 20 to 21 km max on the highways and your car gives 29 km an almost 8 to 9 km difference in mileage because of 100kgs of weight

[Ram]

Originally Posted by humyum

Dude are u kidding about the average part.29 something on the highway .I know its an mpfi 5 speed 800 but alto shares the engine with your 800 and weighs 100kgs more than your 800 but alto gives a mileage of 20 to 21 km max on the highways and your car gives 29 km an almost 8 to 9 km difference in mileage because of 100kgs of weight

Let me let you in on my secret:

Fuel economy has much to do with how you drive,
how and when you change gears and
how early you get into fifth gear (overdrive) and how long you stay there.

The Maruti 800 system will tolerate getting into 3rd gear early and remaining there indefinitely. That encourages a lazy driving style and of course, wrecks fuel economy.

However, you can develop better habits than that. And that will help your fuel economy.

Then again, all my car engines from the Pontiac to the Maruti 800 have maintained like-new compression. The oil and filter is changed with military paranoia every 5,000 km. (4,000 km in case of my Mahindra MM-540). I never make the engine pink and knock under load at low rpm and generally stay close to the peak torque zone.

I always use high octane fuel (ideally BP:Speed, and failing that, at least HP:Power).

Then I always accelerate gently and uniformly,
(driving as if to protect a soft-boiled egg between my foot and the accelerator pedal, from getting crushed).

And lastly I have never allowed any of my engines to ever overheat in its life.

So, bottom line--- While all cars are "nearly alike" (I still don't say, "identical") when they come off the production line, driving habits and maintenance schedules, impact their destiny, hugely later on in their lifespans.

[humyum]

ram i got some questions for u.Even my car needs a tyre change asap but its a carburated maruti 800 1998 model and run 63500 km.The old radials that i have in my car have run around 38000km and are getting puntured due to very less tread thickness.But i got some cost constraints and 7875 is kind of expensive as i will be selling the car in say about 6 to 8 months.Can u suggest me some other tyre company with the same tyre size but less in cost.I am planning of only buying 4 tyres instead of the 5 that u got.Going to keep one of the current lot radials which has a little better tread left as stepney.This will also save me the trouble of stepney not fitting the stepney bay.Please suggest something.
And i did not understand the part where u said that u got the suspension geometry angles realigned.Did u mean wheel alignment?was all this done at the same mrf tyre show in chembur where u got the tyres.As i live in ghatkopar so it will be easy for me to go to the shop u went and get all this done along with the tyres(although of different brand i hope he does stock different company tyres too).Thanks advance

[humyum]

Ram please help dude..waiting for your reply regarding my queries..

[Ram]

Originally Posted by humyum

ram i got some questions for u.Even my car needs a tyre change asap but its a carburated maruti 800 1998 model and run 63500 km.The old radials that i have in my car have run around 38000km and are getting puntured due to very less tread thickness.But i got some cost constraints and 7875 is kind of expensive as i will be selling the car in say about 6 to 8 months.Can u suggest me some other tyre company with the same tyre size but less in cost.I am planning of only buying 4 tyres instead of the 5 that u got.Going to keep one of the current lot radials which has a little better tread left as stepney.This will also save me the trouble of stepney not fitting the stepney bay.Please suggest something.
And i did not understand the part where u said that u got the suspension geometry angles realigned.Did u mean wheel alignment?was all this done at the same mrf tyre show in chembur where u got the tyres.As i live in ghatkopar so it will be easy for me to go to the shop u went and get all this done along with the tyres(although of different brand i hope he does stock different company tyres too).Thanks advance

1. I don't know if the MRF dealer I mentioned, stocks other company tires.
2. Yes I did get mean wheel alignment, and it was done at the same MRF shop.
3. You cannot have 4 big wheels and one small wheel. The Maruti 800 is a front wheel drive. So its rear wheels only freewheel.
   
   Thus it may be tolerable, to mount a smaller diameter tire on one of the rear wheels, especially for limping home after a puncture.
   
   On the other hand, the front wheels are driven by a transaxle (combination of transmission and differential-axle in a single casing).
   
   For the front wheels, it's very important to have both tires of the same diameter. If the tires are of different sizes, their road RPMs will vary, when driving straight ahead. This will cause the differential mechanism to run continuously and wear out.
   
   If you want to mix old and new tires, please buy new tires of the same size as the old ones.

Hope I was able to explain clearly.

[humyum]

Hey ram thanks a ton for the reply.After posting my last thread i was thinking about the rpm variation thing u told me.Could short drives as long as to go the punture fellow cause any harm to the differential.Also i hav heard of space saver tyres used in foreign countries.In their cases what happens when they use that kind of tyre for short distances?
About buying tyres of the same size as mine dude after reading your opinion and review about the new tyres u brought i am just waiting to get my hand on the same rubber u got

[Ram]

Originally Posted by humyum

Hey ram thanks a ton for the reply.After posting my last thread i was thinking about the rpm variation thing u told me.Could short drives as long as to go the punture fellow cause any harm to the differential.Also i hav heard of space saver tyres used in foreign countries.In their cases what happens when they use that kind of tyre for short distances?

About buying tyres of the same size as mine dude after reading your opinion and review about the new tyres u brought i am just waiting to get my hand on the same rubber u got

Short drives to go the punture fellow should not harm the differential, as long as you dont drive more than 50-80 km, and do no more than 60-80 km/hr,
and the oil in the differential is still clean and good.

Space Saver wheels are narrow, large diameter wheels with skinny disposable tires. Designed to economize on dikky space, they're sometimes stored deflated, with an aerosol pressure can to inflate before use. They are often painted bright yellow, red or black to ensure that they cannot be confused with a standard wheel on the vehicle. They are generally restricted to 60 km/hr. Also, being designed for disposable use, they have a very limited amount of tyre tread rubber, and go fully bald in about 250 km.

[humyum]

Thanks Ram the information.It was really helpful.One more thing can u give me the address and phone number of the MRF dealer in chembur from where u got the tyres?Also did he charge you for the balancing and alignment after u got the new tyres?
Also in the current lot tyres i have which are radials 145/70/r12 and the stepney i have kept is the tyre which came with the car.The cross ply thin tyre.What size are those?is there any difference in the sizes of the radial and the cross play as in not the width but the diameter difference which could harm the diffential.

[Ram]

Originally Posted by humyum

Thanks Ram the information.It was really helpful.One more thing can u give me the address and phone number of the MRF dealer in chembur from where u got the tyres?Also did he charge you for the balancing and alignment after u got the new tyres?

Also in the current lot tyres i have which are radials 145/70/r12 and the stepney i have kept is the tyre which came with the car.The cross ply thin tyre.What size are those?is there any difference in the sizes of the radial and the cross play as in not the width but the diameter difference which could harm the diffential.

The address:
Guardex Tyres, Shop No. 1-3, Shiv Enclave, Sindhi Society, CST Road, Behind Chhagan Mitha petrol pump, Chembur, Mumbai 400 071.
Tel: 2729-0123, 2522-1114.

Directions:
When coming from Ghatkopar, take the Eastern Express Hwy(towards Sion) at Amar Mahal. Leave the Eastern Express Hwy before the Kurla flyover, turn left and go to the Chhagan-Mitha pump junction. Cross the junction and proceed towards Basant Park.

Guardex MRF tyres is immediately after Chhagan-Mitha pump on the right. You will have to go some distance past and U-turn and come back as there is no break in the road-divider at Chhagan-Mitha.

Your cross-ply tire:
Your cross ply thin tire is probably 4.50-12. Assuming 100% tire aspect ratio, the section height would be 114.3 mm. That would give a rolling dia. of 533.4 mm, when new. This is 5% taller than your 145/70R12 tires, when new. And it is barely 0.6% smaller than my tires.

So, the calculations show that, my tires restore the original height of the Maruti 800, to what it used to be with cross-ply tires.
However they are a good 27% wider!