Mixing tyre brands - part 3

I understand the reason for a stickier front to prevent washout, and I understand the tread patterns working together to clear water arguments, but that wasnt the problem I had when I mixed a Dunlop D220 front, with a BT020 rear.

What I think the issue was, though I have never seen a front D220 next to a front BT020, is that the curved cross section of the D220 is quite flat. It was a slow tyre to turn, didnt tip into a lean very quickly or hold it very well, and chicken strips on the tyre about 5mm less than other popular tyres for the same lean angle.

The effect this had on the bike was it FELT as if the rear was more willing to drop into a lean than the back. When countersteering what you are essentially doing is steering the tyre away from underneath the bike, so the bike starts to fall in the opposite direction. Once fallen into a lean, the bike rests on the sloped side of the tyre, your bars pivot back round to the direction you are turning, you can relax the countersteer and the tyre rolls through a curve, in the same way an ice cream cone will go in circles if you try to push it along a table.

With this mismatch of tyres, it felt as if the rear tyre was on a steeper sloping side, like a wider steeper ice cream cone, which would turn in tighter circles when rolled on a table. The front didnt want to lean as easily as the back, the bars were staying in the counter steered or straight ahead position right way through the turn and needed constant or increasing counter steer pressure all the way round. The rear felt as if it was kicked out slighly further than it should be, giving the feeling that the bike was about to loose the rear and potentially highside you. When you switched direction from one lean to the opposite lean, it took a lot of counter steer and the rear end seemed to 'pendulum swing' in an exaggerated movement from one side to the other.

So physics experts - does the above make sense? Two different cross sections creating two different diameter 'ice cream cones' with incompatible turning properties? Is this a little known reason to be careful fitting mismatching tyres?

Given that new SVs come on D220's, the front lasts much longer, and the D220 is a very shallow slow turning tyre, I cant be the first and only person who has fitted a quicker turning tyre on the rear of a 4000 mile SV, and left the D220 on the front.

Nobody has a view on this??

It sounds like a reasonable suggestion.

For any give. Angle of lean the two differently angled tyres ought to want to turn the bike at two different angles but I'd imagine it's pretty self correcting in real life.

Originally Posted by Spank86

It sounds like a reasonable suggestion.

For any give. Angle of lean the two differently angled tyres ought to want to turn the bike at two different angles but I'd imagine it's pretty self correcting in real life.

It's just a theory that I have, which basically I've made up, because it's the only way I can explain the way the bike handled.

I don't even know if the cross section of a D220 is indeed shallower than the front would have been had I put a matched pair of BT020's on, so I'd be interested in that if anybody knows.

The D220 did look quite shallow, the chicken strips were really easy to remove without massive lean angles and without running out of ground clearance, and it was definitely a slower front tyre to tip into turns than the Pirelli Diablo Strada's that replaced it at about 7500 miles.

It was self correcting, the bike still went round the corner, but what it felt like was that the correction was being made at the headstock, the only non-fixed pivot point between the D220 on the front and the BT020 on the back.

[Paul the 6th]

We talking like a waffle cone or a conventional 99 cone?

Well it makes sense, had a similar discussion with fallout the other day about chicken strips, one of our bikes had more on the back than the front, the other bike was the other way round.

My theory was that I'd prefer smaller strips on the back, he reckoned he wanted them equal but either way if you're mismatching tyres with different profiles you could wind up running out at one end long before you got anywhere at the other.

To be honest I'm skeptical when people say you can mis match tyres and it'll be fine. Surely it depends on your criteria for fine? I mean yeah 99% of the time it may not be an issue but that 1% is gonna be right when there's an emergency and you're asking your bike to really perform... And that's not a good time to be hitting a tyre mismatch problem and having grip issues.


Of course the same could be said for fitting budget tyres but at least the. The rubber on your bike is working as it should, even if that's not as good as other rubber could do.

Originally Posted by -Ralph-

Nobody has a view on this??

We would if we could bloody understand what you mean lol

Pt6th was thinking along same lines as me so that must be how your op come across Col

He's talking about two tyres that have different curves on them.

So one is more pointy and thin, and the other is flatter and wider.

Originally Posted by Spank86

He's talking about two tyres that have different curves on them.

So one is more pointy and thin, and the other is flatter and wider.

I know mate, just yanking his chain

Originally Posted by specialone

I know mate, just yanking his chain

Barsteward!! I just spent half hour drawing what I meant, and he knew what I meant the whole time!! Saturday he gets me chased by a herd of bulls whilst my motorbike is in pieces on the ground, now this! His tent pegs are so coming out the ground at 4am on the next trip!!