Fatter tyres after motorway scare

[djcat]

Sometimes I take the motorway with the little PCX, usually on sunny weekends or when my car was in for a 6 weeks long transmission change and I had no other way to get around. So one time last frosty week I thought that it might be a great idea to ride to work... down the M4 I went into London, just to eat sh*t that a lorry (truck...) in front of me threw at me from the damp road and I had no power to pass him safely, my white Arai never looked so brown and I was blind before I passed Slough.....on the way back, in the middle of rush hour, I was fine as everybody was doing 60ish until traffic threw out the anchors and I had to come to a complete stop from 60...what a brown pants moment that was!

I know its not the usual way to ride a scooter, but I somehow lost confidence in that thing, brakes seemed inexistant and rubbish at that speed, scooter whobbled violently and I was happy to keep it upright and come to a stop just an inch from the car's bumper.

So beat me up, but I did swear to myself that time to give up the PCX and declare all bikes with less than 500cc and 17 inch wheels unsafe at any time.....until I thought about half the issues I had were grip and that I had issues with that before.

I want to change the skinny IRC ones to fatter tyres and reading a few old posts on here and elsewhere I am thinking about a 120/80 for the rear and a 110/80 for the front, using the K66 from Heidenau.

Can anybody on here pls confirm if that would fit without scraping? I am pretty confident it would by reading on another forum, but just want to make sure.

And no, I will not go on the M4 during rush hour again and keep my motorway excursions to less crowded times...

Thank you!

[you you]

What has tyre widths got to do with the story of your scary ride?

[haildamage]

sorry but both the PCX 125 and 150 are not well suited for the motorway/ freeway. you can run a marathon wearing flip flops but that doesnt make it a good idea!

[khaosaming]

The PCX is a nice little scooter built for comfort at low speeds. Your problem is petty engine capacity combined with average shocks and brakes -- not tyre width.

Actually skinny tyres are good for traction and agility. Fat rear tyres tend to squirm on bad surface more. I know this, because I have a custom bike (Honda Shadow RS VT750). A larger diameter rim would help, but I doubt you can change the wheel size on the PCX.

The PCX should not wobble a lot at all per se. With "wobble" I mean a violent shaking of the handlebar caused by bad frame and oversized engine. A Kawasaki from the '70's would wobble -- not the PCX. The PCX just stops accelerating much sooner. I think what you call a wobble is the effect of high speed traffic creating a strong wind that shakes your scooter, especially if you ride behind a lorry.

If you do a lot of freeway riding, you should consider a bigger scooter -- the SH300 would be just what the doctor ordered.

[djcat]

Good morning! Thank you for your concerns.

I did not ask whether anybody considers the PCX suitable for motorways or not :-P it is not illegal and I did it before. Just not at rush hour traffic, during which time I would have liked to have more power to pass and merge lanes safely and more grip during heavy braking from faster speeds. I had decent sized bikes before and I understand what I got when I bought the PCX.....I don't think I need to explain the correlation between tyre width and grip, some people mounted fatter tyres and I just would like to know if I will have any issues with a 110 in the front and a 120 in the back.

If you know the answer, can you please be so kind and let me know?

Thank you!

[djcat]

The PCX is a nice little scooter built for comfort at low speeds. Your problem is petty engine capacity combined with average shocks and brakes -- not tyre width.

Actually skinny tyres are good for traction and agility. Fat rear tyres tend to squirm on bad surface more. I know this, because I have a custom bike (Honda Shadow RS VT750). A larger diameter rim would help, but I doubt you can change the wheel size on the PCX.

The PCX should not wobble a lot at all per se. With "wobble" I mean a violent shaking of the handlebar caused by bad frame and oversized engine. A Kawasaki from the '70's would wobble -- not the PCX. The PCX just stops accelerating much sooner. I think what you call a wobble is the effect of high speed traffic creating a strong wind that shakes your scooter, especially if you ride behind a lorry.

If you do a lot of freeway riding, you should consider a bigger scooter -- the SH300 would be just what the doctor ordered.

Yes, engine capacity is an issue, but so is grip of those skinny IRCs. At least I do consider 15 mph around a roundabout territory a scooter should be able to master without loosing the front end...and I had exactly that a few weeks ago.

If I brake hard and it slides from side to side from 60mph and the handlebars go left and right, I would describe that as a whobble. Given the PCXs top speed is beyond 60, it needs to be able to do a safe emergency stop from that speed, which it didn't. There were no lorries around when I had to brake hard.

Yes, I do a lot of freeway riding, but I also do a lot of town riding and I appreciate that the PCX is not a handful to handle when parking and I have only a few minutes until my train departs. Besides, my other half doesn't ride bikes beyond 125cc as she only got a CBT.

[khaosaming]

I don't want to sound stubborn or rude. Nor am I am inclined to keep you from changing your tyres the way you want them to be. You seem to have made up your mind already.

When one answers someone's post, it is intended for a wider audience, not just for the original poster. That's why other points of view emerge and might be useful. Feel free to ignore any advice you may find not spot-on in your case.

In my mind you won't get better grip by just getting fat tyres front and rear. The original factory-installed set of tyres by IRC (I have Dunlop TT900F, by the way) might be better designed for durability than grip. A good tyre that uses hard rubber works alright in a warmer climate, but not so under colder circumstances. So, you could change the tyres but not necessarily the size. There must be a ton of other makes with a suitable rubber softness and pattern for your needs.

You might also check your tyre pressures, rear drumbrake adjustment and brake pads. Change of shocks might also improve your ride. The brakes on PCX are not entirely great. They are mere adequate. Changing them is counter-productive, but you could try another brake pad make.

[khaosaming]

It just occurred to me that there was an issue and a recall by Honda to change a certain set of IRC tyres, because they were defective and might split. I'm not sure if it only applied to some PCX150's.

There's a thread about that issue here.

[khaosaming]

I hate to send multiple posts in a row, sorry for that. If only I could edit my earlier posts a little bit longer.

In Finland, the local Honda dealer had IRC Urban Master Snow tyres fitted on their PCX125. This tyre is basically a winter tyre with a good grip on moist roads. The size seems to be 80/80-14 front and 110/80-14 rear. Might be too skinny for your needs, but the shop keeper claimed they were excellent.

Here's a photo:

[you you]

I've never had a bike slide from side to side unless I've locked the rear brake

That, the motorway and the roundabout sliding all sound very dramatic and dangerous.

Those blocky tyres are a find. Useful for those who take their PCXs off road

[khaosaming]

The size seems to be 80/80-14 front and 80/110-14 rear.

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Of course, I tried to say 80/80-14 front and 110/80-14 rear.

Maddiedog, please help and erase that bloody mistake from my post above.

[djcat]

I hate to send multiple posts in a row, sorry for that. If only I could edit my earlier posts a little bit longer.

In Finland, the local Honda dealer had IRC Urban Master Snow tyres fitted on their PCX125. This tyre is basically a winter tyre with a good grip on moist roads. The size seems to be 80/80-14 front and 80/110-14 rear. Might be too skinny for your needs, but the shop keeper claimed they were excellent.

Here's a photo:

Interesting info on the IRCs, they sure weren't made for colder climates either. They feel soft on the touch but when handling anything below 10 degrees C, loose grip.

Great picture, thanks. I want to go for the Heidenau K66 Tyres, I understand these are the best to handle cold temperatures and wet roads and even snow if needed (http://www.advrider.com/forums/showthread.php?t=630322). Not that I intent to do the latter....

So the 110 fits for sure, I may upgrade to the 100/80 or 100/90 for the front then. The combination of just slightly larger rubber with softer more adequate compound might be the best compromise.

[you you]

Don't know if it helps but I ride a lot differently in the wet. No slower really (it is only a scooter) but I do keep the bike more upright on corners and roundabouts by shifting my weight. Id say I avoid heavy breaking but I do tend to do that in the dry too. Just try too keep things smooth and maintain momentum.

Riding like this I don't have any issues over the stock tyres - they are good enough for me.

[Cracksta]

wider tyres dont give more grip (cant remember where i read that from).

the brakes certainly aren't great but good enough to stop, as mentioned, i too ride different when its wet, less lean, more careful etc.

I try to stay away from motorways simply because the bike's engine is not powerful enough to get you out of trouble, probably not as stable as the bigger bikes and the swing you mention, sure you wasnt putting pressure on 1 side of the bar as you come to a halt? I tend to do that so i get a little 'wobble' every now and then, cant blame me, half the time i cant feel my fingers in the cold.

In the city the bike is fine, pull away from the lights easy (until the bigger bikes scream behind you), stable, just got to be careful with the drains on cornering.

I would def not use it again on motorway unless you have to, it will get the job done but not as comfy/safe as you are expecting.

EDIT: last thing is suspension, do i need to say anymore?

[khaosaming]

The combination of just slightly larger rubber with softer more adequate compound might be the best compromise.

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I think you've hit the nail right on the head there. Just don't forget about the tread pattern. A winter tyre must have deeper grooves, a lot of them, for the best grip possible.

[gn2]

At least I do consider 15 mph around a roundabout territory a scooter should be able to master without loosing the front end...and I had exactly that a few weeks ago.

Roundabouts are slippy bastards of things where diesel spills are commonplace.
Wide tyres won't save you from diesel.
As for stability under hard braking on OEM IRC tyres, so long as the pressures are correct and the tyres are not worn (particularly the rear) and the surface is good it should track straight and true.

[uploader]

Grooves on a tire are used more for water displacement then grip

[khaosaming]

Grooves on a tire are used more for water displacement then grip.

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You're right. Grip is also better when the water is removed. After all snow is water. Grooves come in handy at aquaplaning. So, the end result is at all cases a better grip, right?

[maddiedog]

Here's a calculator if you want to experiment with what a size change will do to tire dimensions, which should let you measure and see if the tires will fit: http://www.hondapcx.org/viewtopic.php?f=15&t=5

Khaosaming, I edited your post.

[djcat]

Thanks a lot for all your answers, I am especially impressed with the tyre size calculator - much appreciated.

As my tyres are correctly inflated and certainly not worn out and I was braking with both front and rear (so equal pressures on the handlebars), I still want to change the tyres. I don't blame the bike for having no power, I couldn't expect much from a 125 anyway, I understand that.

Grip I do consider essential at all times though and I believe I did everything anybody could have done to help it regarding smoothness & safety (e.g. safety distance, speed, observation, IPSGA etc.). I do also expect that if its possible to do 60mph on it, brakes, suspension and tyres need to be up to it. I am not perfect, way not, still in hindsight I just don't think I could have done anything to stay safer other than taking the train instead.

Yes, roundabouts can be treacherous, motorways are not a 125cc usual territory, it was wet and cold and I was crossed with the experience to the point of thinking about getting rid of it...but I think I want to give it another chance given its a joy around town and cheap as chips and even comfy for the missus as a pillion. There are people here who cross the world on a PCX, so who am I to mis-judge it like that? I think I can improve its braking and grip with if not larger at least more adequate tyres, so if I do change them I want to try a different size, too.

Did anybody on here try out a larger size? Did it fit all right? What size was it?