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Author Topic: Tire Pressure vs Carry Weight  (Read 1654 times)

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Online DrM

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Re: Tire Pressure vs Carry Weight
« Reply #15 on: November 15, 2020, 10:07:41 am »
@lunkhead: BTW, while I now have hard figures on the maximum allowed weight distribution for front and rear wheels for 36/41 psi (thanks to you for pointing me to the label) I still only have guess information on the normal weight distribution front and rear wheels for 33/36 psi tire pressure.  Do you have any data from Yamaha and the weight distribution for 33/36 psi tire pressure?

Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #16 on: November 15, 2020, 12:56:34 pm »
Thanks for posting the label and calculating the distribution. I have the C-Spec and the label allows for 9 extra lbs up front for a total of 1008 lbs over the other Bolt model's 999 lb limit. The difference is a belted front tire, stiffer fork springs (?) and a more forward lean/seating position.

The 84 lbs you shorted yourself was the LI 67 I was referring to earlier. I don't have any more info relating to the lower pressures but I used a rider weight of about 175 lbs along with your distribution measurements. A 150 lb rider with gear = 175 lbs. I think that's a good approximation of an average light weight rider.
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Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #17 on: November 15, 2020, 02:09:28 pm »
Here's the C-Spec label.

C-SPƎC

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Online DrM

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Re: Tire Pressure vs Carry Weight
« Reply #18 on: November 15, 2020, 04:41:45 pm »
I am going to revise my lower wheel loads for 36/33 rear/front to also be a 150 lb rider on a 60/40 % split rear/front.  But then I will add on 48 pounds of cargo all on the rear wheel, which won't affect the front.  So I will get a similar loading range as you, though slightly different. 

I'm going to re-weigh the bike, and myself on it, and I will likely have to remove something off the front - maybe the windshield and/or maybe the slider bar in the front, as I suspect that at 175 lbs, I am already at or over the 313 lb GAWR for the front. 

If that turns out to be true (that I'm already at or over GAWR on the front), then that might have serious consequences for larger riders than I in that they should be very careful how they modify their bike - with special attention to minimizing any weight gain on the front.


Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #19 on: November 16, 2020, 01:10:01 am »
More calculations:

Rider weight - FR / RR pressure:
175 lbs - 33.0 / 36.0 psi
200 lbs - 33.8 / 36.4 psi
225 lbs - 34.6 / 36.7 psi
250 lbs - 35.3 / 37.0 psi
275 lbs - 36.0 / 37.3 psi (front limit)

Passenger/cargo weight (over rear axle):
For every 49 lbs - add 1 psi to rear

Rear weight limits at GAWR:
245 lbs w/ light (175 lb) rider - add 5 psi
182 lbs w/ heavy (275 lb) rider - add 3.7 psi
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Online DrM

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Re: Tire Pressure vs Carry Weight
« Reply #20 on: November 16, 2020, 01:53:31 pm »
I have substantially revised my tire pressure chart to reflect changes suggested by Lunkhead.  The only thing we have not ascertained completely is the weight distribution to the front and rear tires for 33/36 psi, as we have not weighed a new, unmodified bike, and I don't know whether Yamaha included the fuel or engine oil in its 542 lbs published empty weight.  So if anyone is in the central Texas area or is going through it on an unmodified Bolt, stop in and we'll weigh your bike to see how that distributes to the front and rear tires.

Revised chart below:   

Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #21 on: November 18, 2020, 10:27:23 am »
I updated my chart to include the tire manufacturer's ratings.

« Last Edit: November 22, 2020, 08:13:24 pm by lunkhead »
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Online DrM

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Re: Tire Pressure vs Carry Weight
« Reply #22 on: November 18, 2020, 11:55:25 am »
I updated my chart to include the tire manufacturer's ratings.


Nice chart!  But how did you get a curve in your chart?  I only have two points (per curve) to plot to, which only defines a straight line.  I'd need another point or two to plot a curve.

Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #23 on: November 22, 2020, 07:10:57 pm »
Final update showing approximate curve:

« Last Edit: November 24, 2020, 10:24:24 am by lunkhead »
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Online Sdaniels

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Re: Tire Pressure vs Carry Weight
« Reply #24 on: November 23, 2020, 09:52:02 am »
More calculations:

Rider weight - FR / RR pressure:
175 lbs - 33.0 / 36.0 psi
200 lbs - 33.8 / 36.4 psi
225 lbs - 34.6 / 36.7 psi
250 lbs - 35.3 / 37.0 psi
275 lbs - 36.0 / 37.3 psi (front limit)

Passenger/cargo weight (over rear axle):
For every 49 lbs - add 1 psi to rear

Rear weight limits at GAWR:
245 lbs w/ light (175 lb) rider - add 5 psi
182 lbs w/ heavy (275 lb) rider - add 3.7 psi

Lunk, is this for C-spec or the other models?
2015 C-spec

Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #25 on: November 24, 2020, 12:10:29 pm »
Sdaniels, those are for a rider weight bias 35/65% and the C-spec should be 40/60% shown in the last chart. I need to calculate some useful figures based on it.
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Online Sdaniels

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Re: Tire Pressure vs Carry Weight
« Reply #26 on: November 24, 2020, 01:54:32 pm »
Gotcha
2015 C-spec

Online Sdaniels

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Re: Tire Pressure vs Carry Weight
« Reply #27 on: November 24, 2020, 04:12:10 pm »
Sdaniels, those are for a rider weight bias 35/65% and the C-spec should be 40/60% shown in the last chart. I need to calculate some useful figures based on it.

Moving toward 40/60 would mean slightly lower pressure for the rear tire & slightly higher for the front. I've also done weight removal from the rear & a slight addition on the front. Rear fender dropped about 13 pounds...there's an 11lb difference between the stock exhaust & the slipon.  Fork brace, steering damper, clubman handlebar/risers, 320mm brake rotor w/adaptors & K&N airbox together added about 6 pounds.  Not sure how much it affects the weight bias but it does push it forward more.
2015 C-spec

Offline lunkhead

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Re: Tire Pressure vs Carry Weight
« Reply #28 on: November 24, 2020, 06:29:56 pm »
This is what I get for the C-Spec:

125 lbs - 33.0 / 34.7
150 lbs - 33.5 / 35.2
175 lbs - 34.0 / 35.6
200 lbs - 34.5 / 36.0
225 lbs - 35.0 / 36.4
250 lbs - 35.5 / 36.8
275 lbs - 35.9 / 37.2

« Last Edit: Yesterday at 02:18:03 pm by lunkhead »
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Online Sdaniels

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Re: Tire Pressure vs Carry Weight
« Reply #29 on: November 25, 2020, 12:00:10 pm »
Thanks Lunkhead...oh and fix your typo on the front tire size  8)
2015 C-spec