Topic: Tire Envy. Rear tire enhancement plan...

[mlinder]

Do your homework and you might be able to fit one of these bad boys on your scoot --->

Thanks, but I like to be able to go around corners.

[merc2dogs]

that kickstand is just for looks right?

 For some reason I always think of queen 'fat bottom girls' when I see one of those bikes

  ken.

[gregimotis]

Do your homework and you might be able to fit one of these bad boys on your scoot --->

I think I'll go with the "Help! Flames coming out of my exhaust" mod discussed some weeks ago instead.

[Kamal]

The handling difference when using different size tires than the factory design may or may not be negligible.

When going straight, a different width tire will have no difference, and a taller or shorter tire will affect the front/rear height.  This tends to have some effect on stability and quickness in turning.  The lower the front end, the quicker the bike will turn, but the less stable it will be at high speed.

When leaning the bike over, the width of the tire will make an effect on the attitude of the bike in turns. This is a little more tricky to explain how the handling is affected.

In the end, unless you are looking to roadrace, I would not worry about how the handling will change with different size tires. Case in point...the CHOPPER.

If you are looking to race, who knows, there may be some better or worse resultant geometry by different size tires than the factory designed, and only the racer familiar with his bike will truly know how things have changed.  With the newer superbikes, though, I would tend to stick to factory size tires as the R&D that goes into those bikes' suspension is hard to beat.

[KB02]

Of course, if you want to go wider and eliminate the Brake stay, there is always this option from cycle -X:



Just replace the drum with a disk brake.

It's just about half way down the page before the exhaust.

[eurban]

Yes their rear disc is pretty cool . . . Still will need a brake stay for the caliper tho, and for the price listed you still need a master cylinder and a brake lever assembly.  They probably won't sell too many systems for that $ but sure does look nice.

[gregimotis]

http://www.cyclexchange.net/Honda%20Page.htm



Must buy stuff... must buy camshaft... (wipes drool from lips)

[ProTeal55]

That rear disc setup is killer - but for the $$ they want for it my factory drum stops just fine...

[TwoTired]

In the end, unless you are looking to roadrace, I would not worry about how the handling will change with different size tires. Case in point...the CHOPPER.

I might comment that emergency avoidance maneuvers on the street, have requirements that are very similar to road race conditions.

If you can scrape the pegs in a turn with the stock size tire, it seems you're getting enough traction for it to do the job.

Will an oversize width tire increase the lean angle enough to be of significant benefit to improve cornering ability.

Or, is the oversize tire stricktly a cosmetic desire?

If you fit a wide tyre to a rim thats too narrow it only increases the height of tyre, it wears out faster and it flexes more (which does nothing to improve handling.)
 If you cant fit wider rims, stay with a tyre thats close to stock size. If you have a look at rim width on G F 250 you'll see its wider than stock 750 ( probably 2.50 X 16 compared to 1.85 or 2.15 x18)
PJ

I heartily agree with this. 
But, if indeed the chopper look is the goal, handling, performance and wear aren't part of the decision making process, are they?

Cheers,

[mlinder]

I too was very concerned about reducing the performance of going with a non-stock size tire on the back.
But, as I said, the tire guy measured the 20 year old 110, and the new avon 110 was quite a bit narrower. The old tire was much closer to the new avon 120, so we went with that. Seems ok so far. Still scraping off the molding compound in the corners, but I only have about 1.5" lef tot go to the edge of the tire.
Handling, braking, and ride quality vastly improved over the (very) old tire.

[TwoTired]

When you modify your bike from stock, you become the responsible engineer.  If you don't need help from the tire industry, then the following will be of no help to you at all.  I will re-emphasize the need to match tire to manufacturer recommended rim width.  If the tire manufacturer says their tire works properly on a 1.85 rim, then you are good to go.  The tire jock at the store will happily sell you bigger tires, as there is usually more profit built in the sale of these.  I won't comment on the engineering skills of the "tire guy".
There is a difference in profiles between the old inch rated tires and the metric specified tires.  This is likely why there isn't a direct inch to metric size conversion. (My educated guess anyway) eg..
Metric    Alpha    Inch               Actual nearest conversion
80/90       MH90    2.50/2.75   ~3.25
90/90       MJ90    2.75/3.00     ~3.50
100/90    MM90    3.25/3.50     ~4.00

http://www.cycleshopusa.com/motorcycle_tires.htm
...has a more expansive converter chart:
MOTORCYCLE TIRE SIZE MARKINGS
Motorcycle tires are manufactured in a number of different countries with differing requirements in terms of load, dimensions and speed ratings. This has resulted in various size markings. The following chart gives a guide to the relationship between various size markings.
THIS CHART DOES NOT IMPLY EXACT COMPARISONS.   STREET MOTORCYCLE TIRE SIZE CONVERSION CHART
FRONT MOTORCYCLE TIRES
Metric Alpha Inch
80/90 MH 2.50/2.75
90/90 MJ90 2.75/3.00
100/90 MM90 3.25/3.50
110/90 MN90 3.75/4.00
120/80   4.25/4.50
120/90 MR90 4.25/4.50
130/90 MT90 5.00/5.10
REAR MOTORCYCLE TIRES
Metric Alpha Inch
110/90 MP85 4.00/4.25
120/90 MR90 4.50/4.75
130/80   5.00/5.10
130/90 MT90 5.00/5.10
140/80   5.50/6.00
140/90 MU90 5.50/6.00
150/80 MY85 6.00/6.25
150/90 MY85 6.00/6.25

[cafehonda]

I am running an Avon am18 supervenom 140/80 tire on a stock rear rim. It fits, no clearance problems, minimum width rim for tire. Can't say how it is wearing because I bought v speed rated sprint compound (very soft compared to street rubber).

[mlinder]

TT, looking at the specs for the tire I got, my rim is quite a bit small (by over half an inch), yet even their 110 is listed for a 2.15 to 2.5"

However, Avon specifies this exact tire for the K0, namely "120/90-18 65V"

So i dunno why they would post two different specs like that. They also correlate 4.00 as 120's, not 110's, in their personal conversion.

I'm not disagreeing that tire size should be as close to spec as possible, but if a tire manufacturer recommends this size for this particular bike, I hope I can trust them in their assessment.

[eldar]

Well I would think the tire manufacturer should be the final answer as they know their tires and what they can do. If they say such and such tires should fit that rim, then it should as they designed the tire.

[TwoTired]

So i dunno why they would post two different specs like that. They also correlate 4.00 as 120's, not 110's, in their personal conversion.

I can only speculate with that dichotomy.  Having been inside large corporations, I  know that marketing departments do not always follow engineering department recommendation or specifications.

Marketing may have weighed the inputs from the engineering dept., the public demand, the current product offerings, and a risk assessment from the legal dept., and then written their own fitment recommendations to enhance company profitability.

I can almost hear the conversation, based on my own "discussions" with marketeers.

A short play by TwoTired:
Curtain rises:
Setting: Conference room at Corporate HQ.  All actors seated at large wooden table, able to seat 10 more than the mere 3 present.  Two are in business suits.  One is in dark pants and a white shirt, pens bristle from the shirt pocket.  Coffee cups, note pads, and pens at the ready, the discussion ensues.

Marketeer:  Since we've discontinued the "Spitvenom Slider" (TM) tire for profitability reasons, what are we going to put on the tire recommendations chart, so we can still sell into 100% of the tire market?"

Engineer: "Well, here's the chart with all the bikes crossed off where our new tires won't work as designed."

Marketeer: "What? Why won't our new tires fit on these bikes?"

Engineer: "Well, you can get them on, but the tire shape isn't right."

Marketeer: "Oh, they look ugly, huh?"

Engineer: "No, they look just fine, they're just squishy (this is a technical term for Marketeers) while riding."

Marketeer: "Can't you just put more air pressure in them?"

Engineer: "Yes, but that makes them wear out faster in the middle, they square off and really perform much worse over time than when new."

Marketeer: "So they have to buy tires more often?"

Engineer: "To maintain best performance, yes."

Marketeer: "Seems like a good thing!  That could help sales!"

Engineer: "No so good for the buyer or our reputation."

Marketeer: "That's not good.  Legal, what's our exposure to mismatching tires?

Legal: "Very low risk. The old bike population is very small and there are few sales into that area anyway.  The idea that any misapplication of tire would result in legal repercussions is remote, at best.  Any public claims to our detriment can easily be quashed with slander suit threats.  And no court would ever find true liability from mere customer claims. "

Engineer: "But, it's wrong.  It doesn't work like it should."

Marketeer: "Hey, it's paying the bills and your salary.  Just do your job. We'll put your data in the spec sheet.  We'll take care of the recommendation chart, which won't be your responsibility."

Legal: "Sounds like a workable solution."

Engineer: " But..."

Marketeer: "Okay, issue resolved, and we have an action plan.  Let's get to work.  Meeting adjourned."

Engineer: "But... hey, where are you all going?"

Sounds of engineer sitting alone in large conference room gazing out large window and contemplating recent events, occasionally sipping his coffee...

Engineer: "I wonder how much longer I'll have this job?"

Curtain falls:

[dusterdude]

i`d give that a tony tt.

[mlinder]

So i dunno why they would post two different specs like that. They also correlate 4.00 as 120's, not 110's, in their personal conversion.

I can only speculate with that dichotomy.  Having been inside large corporations, I  know that marketing departments do not always follow engineering department recommendation or specifications.

Marketing may have weighed the inputs from the engineering dept., the public demand, the current product offerings, and a risk assessment from the legal dept., and then written their own fitment recommendations to enhance company profitability.

I can almost hear the conversation, based on my own "discussions" with marketeers.

A short play by TwoTired:
Curtain rises:
Setting: Conference room at Corporate HQ.  All actors seated at large wooden table, able to seat 10 more than the mere 3 present.  Two are in business suits.  One is in dark pants and a white shirt, pens bristle from the shirt pocket.  Coffee cups, note pads, and pens at the ready, the discussion ensues.

Marketeer:  Since we've discontinued the "Spitvenom Slider" (TM) tire for profitability reasons, what are we going to put on the tire recommendations chart, so we can still sell into 100% of the tire market?"

Engineer: "Well, here's the chart with all the bikes crossed off where our new tires won't work as designed."

Marketeer: "What? Why won't our new tires fit on these bikes?"

Engineer: "Well, you can get them on, but the tire shape isn't right."

Marketeer: "Oh, they look ugly, huh?"

Engineer: "No, they look just fine, they're just squishy (this is a technical term for Marketeers) while riding."

Marketeer: "Can't you just put more air pressure in them?"

Engineer: "Yes, but that makes them wear out faster in the middle, they square off and really perform much worse over time than when new."

Marketeer: "So they have to buy tires more often?"

Engineer: "To maintain best performance, yes."

Marketeer: "Seems like a good thing!  That could help sales!"

Engineer: "No so good for the buyer or our reputation."

Marketeer: "That's not good.  Legal, what's our exposure to mismatching tires?

Legal: "Very low risk. The old bike population is very small and there are few sales into that area anyway.  The idea that any misapplication of tire would result in legal repercussions is remote, at best.  Any public claims to our detriment can easily be quashed with slander suit threats.  And no court would ever find true liability from mere customer claims. "

Engineer: "But, it's wrong.  It doesn't work like it should."

Marketeer: "Hey, it's paying the bills and your salary.  Just do your job. We'll put your data in the spec sheet.  We'll take care of the recommendation chart, which won't be your responsibility."

Legal: "Sounds like a workable solution."

Engineer: " But..."

Marketeer: "Okay, issue resolved, and we have an action plan.  Let's get to work.  Meeting adjourned."

Engineer: "But... hey, where are you all going?"

Sounds of engineer sitting alone in large conference room gazing out large window and contemplating recent events, occasionally sipping his coffee...

Engineer: "I wonder how much longer I'll have this job?"

Curtain falls:

[gregimotis]

I wouldn't want to sidetrack an interesting conversation, but are the stocks rims on the F1 same width as the K's?

[CB750R]

Guess I should have added, my 160mm is on a different' rim/brake setup, as seen in my Avatar, I have a fat 1/4" between my chain and tire so my chain guard is beeing reworked, as it now hits the new shocks and the tire!!! I think I'd have tire on chain issues before tire on swingarm in my case!!   I saved over 50lbs in rotational weight swapping out my Comstars and super thick discs for more modern wheels and brakes!!! by the sounds of it 

[mlinder]

OK, as I do more research, I'm getting more and more confused. The dunlop stickey-style replacement at the time these were released was also a 120 rear. I measured the width of my rear rim, though I'm not sure WHERE they measure it to/from to get the reading, inside or outside of the lips. In any case the outside of mine is about 3 3/8", inside, I'd Imagine, is no less than 3". Avons recommended rim width is as follow for their 120/90 18" rears..


It appears that I'm right at, or even slightly larger than, the MAX rim width that these tires are designed with.
So... wtf?
Lot's of FUD.

/edit: OK, are D.I.D. rims stock for this K0? Cause that's what I have on this bike.

[TwoTired]

My Cb550 rear rims measured 2.8 outside width.  The rim edges are rolled/folded and form a rim metal width of about .5 inches per side.  If you then subtract 1 in. from the outside measurement, you get pretty close to the 1.85 in inside width spec. stated for my CB550 bike.

Assuming you have spoke wheel rims of similar construction, you would subtract about an inch to obtain the inner rim width, or 2 3/8 inch from your stated measurement.  Standard rim widths are 2.15 inch or 2.50 inch.  If you suspect your rear rim is a stock size offered in 69-70 ( I think D.I.D. was a Honda supplier), I would assume it is a 2.15 width rim.

Tire manufacturers state the rim width their tire is to seated into, as that sets the bead to bead distance across the rim.

Bet you didn't want to read that.   Sorry.

Cheers,

[mlinder]

My Cb550 rear rims measured 2.8 outside width.  The rim edges are rolled/folded and form a rim metal width of about .5 inches per side.  If you then subtract 1 in. from the outside measurement, you get pretty close to the 1.85 in inside width spec. stated for my CB550 bike.

Assuming you have spoke wheel rims of similar construction, you would subtract about an inch to obtain the inner rim width, or 2 3/8 inch from your stated measurement.  Standard rim widths are 2.15 inch or 2.50 inch.  If you suspect your rear rim is a stock size offered in 69-70 ( I think D.I.D. was a Honda supplier), I would assume it is a 2.15 width rim.

Tire manufacturers state the rim width their tire is to seated into, as that sets the bead to bead distance across the rim.

Bet you didn't want to read that.   Sorry.

Cheers,

No, that's good information, and I did want to read that. It lessens the confusion. That put's my rim at the absolute minimum width for said tire, which is ok, but not optimum. I'll rectify the mistake next time I get new tires.