Tyre size - How much can I change without impacting handling

[Harryc]

I've had my V7ii Special for a couple of months now. Planning for new tyres in about 12 months time.

I'm currently running Pirelli Sport Demon (Rear) and Pirelli Phantom (Front).

Next set of tyres I'm thinking about something with a scrambler look. Maybe Heidenau K60 or Shinko E700. I've read the thread here: https://wildguzzi.com/forum/index.php?topic=85669.0 , but I'm still keen on going fatter on the front tyre.









The K60s come in stock sizes - 110/80-18 and 130/80-17, but they are a physically bigger tyre than the road tyres I have on now. About 11mm larger OD front and 19mm larger rear. This looks like it will increase my trail measurement by about 1.7mm (109 to 110.7mm).

The Shinkos will have a bigger effect. I can get these in 4.60-18 and 5.10-17, which are close in size to the existing tyres, +14mm Front, and +7mm Rear. Using these will increase the trail to 113.7mm.

My final option is a larger set of K60s - 120/80-18 Front, 120/90-18 Rear. These would give me +29mm OD Front, +27mm OD Rear. The front is 31mm wider than stock, and will be a tight squeeze under the mudguard, but it should fit. This option pushes my trail measurement out to 116.8mm.

Both the E700 and smaller K60 Front will be around +20mm wider than the current. Rears are about +10mm for the small K60, -2mm for the  E700 and no change for the taller K60. The smaller/wide K60 rear will give around 2mm clearance to the driveshaft on the right hand side.

My options that I'm looking at are:
                                     Front              Rear
                                Width   OD    Width  OD       Trail
K60 Standard Sizes:   +20     +11     +10  +19       +1.7mm (110.7)
Shinko Inch Sizes       +20     +14     -2     + 7        +4.7mm (113.7)
K60 Over Size            +31     +29      0      +27       +7.8mm (116.8)

So, my question is - Will I notice +2mm or +5mm or +8mm change in trail. I understand that increasing trail should make the bike more stable and slower to turn-in. Is this change going to be noticeable to a novice rider like me? How will the effect of the change in trail compare to the +20mm or +30mm width on the front tyre?

Oh, and if you need to tell me I'm a fool for doing this, I can't say you're wrong, but I like what I like. Tyres have always been a bit like boobs for me - Always have to take a look, and always wish they were just a little bigger...

Thanks,

[twowheeladdict]

Every change will impact handling.   

Some will impact handling positively, while some will impact handling negatively.

Changing tread pattern will impact handling.  Changing diameter of the tires will impact handling.  Changing width of the tires will impact handling.

Set the bike up for the type of riding you want to be doing.

If you are riding the twisty roads then a slightly larger rear diameter and/or slightly smaller front diameter will help with turn in.

If you are riding gravel and off road, then scrambler tires will aid in traction, but if you are mostly pavement you will give up traction.

If you are just a mellow putt around kind of rider then you probably won't notice any difference.

[oldbike54]

 You're a boob for wanting larger tyres .

 Dusty

[pete roper]

By changing the profiles you will take something that handles reasonably for a 1970's motorbike and turn it into something that handles like a fridge. Best thing would be to fit narrower rims and skinnier tyres if you want it to handle better.

If you just want it to 'Look Cool'? That's fine but don't expect it to be a better, or even good, motorbike.

Pete

[Harryc]

Thanks for the quick feedback folks. I think I knew this would be the answer. At least I've got around 12 months to get over my obsession with big .. tyres..

Cheers,

[Perazzimx14]

Tire size is not constant across manufacturers. So 120/70-17 between Michelin/Shinko/Pirelli/Metzler etc will all be a little different.

[wirespokes]

Larger tires will make turning-in sluggish, if not hard work. It's like going from power steering to non power steering with half flat tires.

I haven't found dual sport tires to impact cornering grip particularly unless they're very aggressive knobbies. Or pushing it to the limit. For normal street riding I've had plenty of traction, even in the wet.

I don't know if larger tires will or won't fit your bike, but I'd recommend staying with the specified sizes.

[twowheeladdict]

By changing the profiles you will take something that handles reasonably for a 1970's motorbike and turn it into something that handles like a fridge. Best thing would be to fit narrower rims and skinnier tyres if you want it to handle better.

If you just want it to 'Look Cool'? That's fine but don't expect it to be a better, or even good, motorbike.

Pete

Pete, not sure how many 2009 and newer V7s you have ridden, or how many modern bikes you have ridden, but IMO, you are spot on with the way my 2010 V7 café classic rode.  The V7III on the other hand rides as well as a modern standard bike.  I feel no difference in handling between this bike and my '15 Yamaha FZ-07.  Now with the suspension upgrades the V7III handles better than my FZ-07.

Peace. 

[twowheeladdict]

Larger tires will make turning-in sluggish, if not hard work. It's like going from power steering to non power steering with half flat tires.

I haven't found dual sport tires to impact cornering grip particularly unless they're very aggressive knobbies. Or pushing it to the limit. For normal street riding I've had plenty of traction, even in the wet.

I don't know if larger tires will or won't fit your bike, but I'd recommend staying with the specified sizes.

Did you mean to write wider tires?   

Larger in width vs larger in diameter provide different results.  Larger in both areas and you have a great beach tire.  LOL!

[Rusnak_322]

Go for it. You are not getting a tattoo, meaning that if you don't like them, you can always change them. those tires are cheap - especially the Shinko.

Doesn't sound like anyone here has any real experience to give you. I have put big fat knobbie tires on a street bike and yes, it doesn't handle the same. It also takes 5 mins to feel normal and after a day, you would feel at home on them. But I have a few very diffferent bikes, and I have ridden street, track, dirt, dual sport and vintage bikes so I am used to swapping from bike to bike.

I am guessing that by picking a V7, you are not looking to drag your knee in turns. As long as you understand the limitations, there isn't any reason to not try it other than the $. 

Then post a before and after ride report to let others know what you thought.

[twowheeladdict]

Go for it. You are not getting a tattoo, meaning that if you don't like them, you can always change them. those tires are cheap - especially the Shinko.

Doesn't sound like anyone here has any real experience to give you. I have put big fat knobbie tires on a street bike and yes, it doesn't handle the same. It also takes 5 mins to feel normal and after a day, you would feel at home on them. But I have a few very diffferent bikes, and I have ridden street, track, dirt, dual sport and vintage bikes so I am used to swapping from bike to bike.

I am guessing that by picking a V7, you are not looking to drag your knee in turns. As long as you understand the limitations, there isn't any reason to not try it other than the $. 

Then post a before and after ride report to let others know what you thought.

 

[Diploman]

The KTM 390 community has been through - at length - the issue of tire size on the 390 Duke and the RC 390 (faired racing variant of the 390).  Both come with a rear tire of 150/70 x 17, a size patently too wide for an agile, lightweight (326 lbs dry) roadster, clearly intended to present a "macho" look bigger than the rear tire of all three Japanese <400cc competitors, which mount 140/70 x 17 or 130/70 x 17 rears.  The KTM and all three Japanese rivals (Honda, Yamaha and Kawa) all have the same size rear wheel.  The Japanese engineers all opted for a tire smaller than KTM's OEM 150.  There was a movement among primarily young and inexperienced KTM owners to mount bigger, 160/70 x17 tires on the 390 Duke, mainly to achieve an even more macho appearance.  The RC 390 racers, however, quickly squelched this impulse by pointing out that, in real world racing conditions, traction and handling were improved on the track by shifting to a smaller rear tire.  An oversized tire on a rim designed for a narrower tire is squeezed into a shape incompatible with the designed profile, thereby losing contact area when leaned over and wearing the center faster when riding straight up.  The consensus turned out to be that 130/70 x17 was the ideal size for the 390's rear tire.

Shortly thereafter, Michelin marketed the Pilot Street radials, a set designed expressly for this <400 class of bikes: front 110/70 x17, rear 130/70 x 17.  This is what I am currently running on my 390 Duke, and I must say they are more comfortable, more agile, longer wearing and sticker than the OEM tires.  Moral of the story: The only benefit for fitting oversized tires is in creating an cosmetic tough, macho look in the eyes of some who disregard function.  The engineers who design and test bikes are no fools:  The stock tires are nearly always the size that works best for the bike.  Pete is entirely correct: You will do nothing but degrade the handling and traction of your bike by fitting oversized tires.  Stick with stock sizes. 

[Harryc]

Thanks again for the feedback. I think I'm going to ignore all the good advice, and listen to Rusnak_322. At the worst I'll have wasted $350 (Australian Pesos) on the Heidenaus. I'll post the results when I make the change over - likely about 12 months so don't hold your breath.

[TN Mark]

The oem front tire on my bike is a 130/70R18. Many owners, me included, have switched to a 160/60. The 160/60 is the biggest tire that will fit between the fender stays etc. It also, IMHO, handles so much better and feels so planted. I can't imagine purposely going back to a 130/70.

The 160/60 is a rear tire mounted backwards to be used in the front.

The oem rear tire on my bike is a 180/60R16. Many owners, me included, have switched to a 195/55 run flat car tire. I only have 1000 miles on the car tire but so far, I'm liking it, a lot.

It's good to have options and like has been posted, it's not a tattoo. If you don't like your choice, try something else the next time or sooner if need be. Tire sizes and types, like tattoos, aren't compulsory.

Every change in tire size/type, suspension etc will most definitely effect handling. Some for the better and some for the worse. Ask those who have actually done what you're considering for their input. Most that will respond likely haven't made the change you're considering but could still likely be strong in their opinion of it none the less.

[Guzzistajohn]

I sure wouldn’t expect any positive influence from the over analyzers around here. You’re probably not breaking any land speed records or even racing Moto gp on your small block anyway. Have fun enjoy your 🏍

[Gappy]

Keep in mind that putting on a larger tire increases centrifugal mass and your breaking power will be reduced with OEM brakes. I have tried this sort of thing only to go back to stock. Rear tires are not as sensitive to a small change in size. The front tire is very sensitive to profile and width changes in braking and handling characteristics . I was luck to get some used tires from a bike shop to try before I made a commitment to new oversized tires. I suggest that you do the same if you can to see if you like it. Good Luck.

[oldbike54]

The oem front tire on my bike is a 130/70R18. Many owners, me included, have switched to a 160/60. The 160/60 is the biggest tire that will fit between the fender stays etc. It also, IMHO, handles so much better and feels so planted. I can't imagine purposely going back to a 130/70.

The 160/60 is a rear tire mounted backwards to be used in the front.

The oem rear tire on my bike is a 180/60R16. Many owners, me included, have switched to a 195/55 run flat car tire. I only have 1000 miles on the car tire but so far, I'm liking it, a lot.

It's good to have options and like has been posted, it's not a tattoo. If you don't like your choice, try something else the next time or sooner if need be. Tire sizes and types, like tattoos, aren't compulsory.

Every change in tire size/type, suspension etc will most definitely effect handling. Some for the better and some for the worse. Ask those who have actually done what you're considering for their input. Most that will respond likely haven't made the change you're considering but could still likely be strong in their opinion of it none the less.

 Just curious , why put a car tire on a high dollar motorbike ? If economy is the goal buy a cheaper motorbike . The only car tire shod bike I ever rode was like riding a hippo , of course maybe not needing to put your fut down at a stop is important to you 

 Dusty

[twowheeladdict]

Just curious , why put a car tire on a high dollar motorbike ? If economy is the goal buy a cheaper motorbike . The only car tire shod bike I ever rode was like riding a hippo , of course maybe not needing to put your fut down at a stop is important to you 

 Dusty

Reads more like a judgement disguised as curiosity.   

[oldbike54]

Reads more like a judgement disguised as curiosity.   

 It is a judgement . Sorry , putting a car tire on a motorbike is a false economy . Yeah , I have heard all of the arguments supporting the use of car tires , none of them hold water.

 Dusty

[twowheeladdict]

It is a judgement . Sorry , putting a car tire on a motorbike is a false economy . Yeah , I have heard all of the arguments supporting the use of car tires , none of them hold water.

 Dusty

I agree.  Whenever I have cornered a car tire guy alone and had a serious conversation with them, they admit that it takes getting used to.  I have yet to see a car tire on a sport bike so riding style might have something to do with accommodating it.  I want to believe that the engineers who chose the tire sizes for a particular bike did it based on performance and not economy.

It is not unlike bikes with 230 fat rear tires, or bikes with ape hangers, or bikes with stretched swingarms or all the other things people do for looks, etc.