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MG · 04-25-2011, 10:49 AM

Query Approved

**jd666** · 04-25-2011, 11:34 AM

^^ can you get a measurement of the OD ( overall diameter) of both tyres for an idea??

**Samarth 619** · 04-25-2011, 12:09 PM

120/80 to 120/90 will raise height by 12mm, if the new tyre's rim area is same as old one's. If it is not the same, then read on...

Ashwin, it is not confirmed that tyre change WILL result in re gearing. Yes, it happens, but not always. For example, People installing FZ's 140/60 on their Pulsar 220s don't feel any change in gearing.

Reason is that the wider tyre was meant for wider rim of FZ, but on narrow rim of P220, it gets squeezed and gives greater height (Rubber expands and contracts depending on the rim). Hence, 140/60 gives almost the same ride height as P220's 120/80, due to rim difference.

So, my suggestion is that you notice speeds now, in 5th gear, at different rpm's like:

3 krpm: 50 kmph
4 krpm: 64 kmph
6 krpm: xx kmph
8 krpm: xxx kmph

And then go for the tyre change first. Then tell me what speeds show up at these rpm's. Then we can decide what gearing to use exactly through precise calculations.

I'll be keeping a watch on this thread...

NOTE: Even P200's 38 teeth fits your bike. P180 UG4's 39 teeth might fit. Karizma's 40 teeth will also fit but that might overkill.

**Praful** · 04-25-2011, 12:34 PM

First change the rubber and see if you want to change the rubber in the first place!

Changing over the 37T sprocket will not completely return back your acceleration. An approx calculation here, Sirac gives you +5 Kmph in each RPM, and using the 37T will give a drop of -3 Kmph in each RPM. So over all you will still be a bit taller geared!

That being said, keep the Sirac and ride for about 1K kms and then decide if you want to up the acceleration!

**ashwin208** · 04-26-2011, 08:06 PM

Originally posted by jd666 View Post

^^ can you get a measurement of the OD ( overall diameter) of both tyres for an idea??

yup here is the measurement -
rim dia - 17inch = 431.8mm
total dia with 120/80 (stock tire)= 431.8+96 = 527.8mm
total dia with 120/90 (michelin sirac) = 431.8+108 = 539.8mm

Originally posted by Samarth 619 View Post

120/80 to 120/90 will raise height by 12mm, if the new tyre's rim area is same as old one's. If it is not the same, then read on...

Ashwin, it is not confirmed that tyre change WILL result in re gearing. Yes, it happens, but not always. For example, People installing FZ's 140/60 on their Pulsar 220s don't feel any change in gearing.

Reason is that the wider tyre was meant for wider rim of FZ, but on narrow rim of P220, it gets squeezed and gives greater height (Rubber expands and contracts depending on the rim). Hence, 140/60 gives almost the same ride height as P220's 120/80, due to rim difference.

So, my suggestion is that you notice speeds now, in 5th gear, at different rpm's like:

3 krpm: 50 kmph
4 krpm: 64 kmph
6 krpm: xx kmph
8 krpm: xxx kmph

And then go for the tyre change first. Then tell me what speeds show up at these rpm's. Then we can decide what gearing to use exactly through precise calculations.

I'll be keeping a watch on this thread...

NOTE: Even P200's 38 teeth fits your bike. P180 UG4's 39 teeth might fit. Karizma's 40 teeth will also fit but that might overkill.

ill be keeping the stock rim .. which is why Im looking at 120 section tires because its optimum for the 220 rim ..
and just for your information , on stock tire here are the speeds/rpm values on 5th gear:
4k - 60 or 61 kmph
6k - 90 kmph
8k - around 120 ish

Originally posted by Praful View Post

First change the rubber and see if you want to change the rubber in the first place!

Changing over the 37T sprocket will not completely return back your acceleration. An approx calculation here, Sirac gives you +5 Kmph in each RPM, and using the 37T will give a drop of -3 Kmph in each RPM. So over all you will still be a bit taller geared!

That being said, keep the Sirac and ride for about 1K kms and then decide if you want to up the acceleration!

Actually the fi sprocket will be fine .. A little tall gearing is always welcome ..

^@ all , thanks for all your input guys .. Will update this thread when i change over to SIRAC ..

**Samarth 619** · 04-27-2011, 11:02 AM

ill be keeping the stock rim .. which is why Im looking at 120 section tires because its optimum for the 220 rim ..
and just for your information , on stock tire here are the speeds/rpm values on 5th gear:
4k - 60 or 61 kmph
6k - 90 kmph
8k - around 120 ish

You didn't get my point. I'm not saying anything about a rim change. What I meant is that, it is not necessary that the Sirac tyre is meant for the P220 rim. It may expand or contract more. Its rim area may or may not be same as your older tyre.

Anyways, I suggest you get the tyre changed first. We'll do the calculations later.

**Shreeni0403** · 04-27-2011, 11:57 AM

Also consider that rubber will wear off with usage. And a bit tall gearing shouldn't really hamper much of your performance.

**Mecho** · 04-27-2011, 10:37 PM

Pulley physics dude.. Higher the diameter, or larger the sprocket / wheel (whatever) Lesser the leverage.. Hence a marginal reduction in pick-up (Torque) But might help in top speeds which depends on sme other fctors of the new element

**motormania** · 04-27-2011, 11:03 PM

Originally posted by Samarth 619 View Post

120/80 to 120/90 will raise height by 12mm, if the new tyre's rim area is same as old one's. If it is not the same, then read on...

Reason is that the wider tyre was meant for wider rim of FZ, but on narrow rim of P220, it gets squeezed and gives greater height (Rubber expands and contracts depending on the rim). Hence, 140/60 gives almost the same ride height as P220's 120/80, due to rim difference.

.

Rubber itself doesnt expand or contract here in this case.

The part of the FZ tyre which you are saying gives better ride when put on a pulsar's rim, was never meant/designed to take the load of a sidewall. You cannot simply slap on larger tyres on thinner rims and claim to gain sidewall height. In that case, the reverse should apply when skinnier tyres are put on wider rims

**ashwin208** · 04-30-2011, 08:51 PM

So in case i'm changng sprocket , should i change the entire set ( front , rear sprocket and chain ) ? The chain and sprocket set wore out prematurely for me and it has been changed @ 12k kms ( currently done 15k ).. Some people feel that the sprockets and chain should all be changed in one go ..

And how about using the Sirac as tubeless ?? I searched the tires thread but there is no one to clearly say "yes no prob" .. So can I use the sirac as a tubeless without absolutely any problems ??
What do you guys feel ??

**motormania** · 04-30-2011, 11:04 PM

Originally posted by ashwin208 View Post

So in case i'm changng sprocket , should i change the entire set ( front , rear sprocket and chain ) ? The chain and sprocket set wore out prematurely for me and it has been changed @ 12k kms ( currently done 15k ).. Some people feel that the sprockets and chain should all be changed in one go ..

And how about using the Sirac as tubeless ?? I searched the tires thread but there is no one to clearly say "yes no prob" .. So can I use the sirac as a tubeless without absolutely any problems ??
What do you guys feel ??

I know of at least 4 different P220s using Sirac as a tubeless tyre with absolutely no problem. Couple of the bikes have seen really harsh riding conditions while on tours and the tyres performed really well, just as they are expected to.

**ARNandal** · 05-01-2011, 02:06 AM

Hi! guyz... I too run on Michellin Sirac 120/90-17 on my p180 ug3...

Can it be run tubeless? How do will we fill air?

**ashwin208** · 05-01-2011, 01:07 PM

Originally posted by motormania View Post

I know of at least 4 different P220s using Sirac as a tubeless tyre with absolutely no problem. Couple of the bikes have seen really harsh riding conditions while on tours and the tyres performed really well, just as they are expected to.

Yeah I also checked with Praful Tripathy and his sirac has been Leh tested as tubeless

should be changing it sometime next week Ill keep you guys posted ..

**Shreeni0403** · 05-01-2011, 02:53 PM

Even I have recently put Sirac as TL on my ZMR !!

Announcement

Michelin SIRAC - compensating loss in torque by using bigger sprocket ?

Michelin SIRAC - compensating loss in torque by using bigger sprocket ?

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