Topic: Tire Change / Dunlop D404 - K-70

[mrmach5]

Recently made a tire change on my 75 CB550k. The bike has appox 19k on it. The tires I replaced were Dunlop D404's, 100-90-19 on the front, 110-90-18 on the rear. Replaced them with Dunlop K70's for their vintage look, 3.25-19 on the front, 4.00-18 on the rear.
Odd thing is that since I made the change, the bike wants to turn in,, especially at low speed, so does not track at a normal rate. I'm adjusting to it, and I wouldn't say its to a dangerous point but does feel uncomfortable. Now I'm regretting not buying K81's instead, have hade good results with them in the past.
Anyone else experienced this ??

[greenjeans]

More of a squared off profile.  A little abrupt especially if you've been riding a more modern profile tire.  I find that they wear quickly in the middle, making things worse. 

[Stev-o]

The K70 is not known to be a great tire. What pressure you running?

[BobbyR]

Tire pressures are critical with these old suspensions. Try adding one extra lb to each tire and test ride. Hopefully this will make it more stable.

With a vintage profile you may get vintage handling which is not very good.

[brewsky]

  The tires I replaced were Dunlop D404's, 100-90-19 on the front, 110-90-18 on the rear. Replaced them with Dunlop K70's for their vintage look, 3.25-19 on the front, 4.00-18 on the rear.
Odd thing is that since I made the change, the bike wants to turn in,, especially at low speed, so does not track at a normal rate.  .........Anyone else experienced this ??

I did the exact opposite.....replaced the old metric sized set (Bridgestone I think) with the same size K70's as you on my '78.

Mine is absolutely neutral in curves and tracks straight as an arrow.

I did replace the steering bearings with tapered at the same time, though.

[b52bombardier1]

I am in the process of returning my recently purchased K70 3.25 x 19 inch front tire. It has a white rubber stripe around the entire circumference of the tread face almost an eighth of an inch wide.

This stripe does not scratch off or sand off with sandpaper.  It's almost as if they wanted to make this tire have raised lettering or white walls and then changed their mind. The Motorcycle Superstore did not argue with me at all when they saw the picture.

I wanted the vintage look but I'm disappointed to hear about the turning performance. It can't be any worse than the rock hard 40-ish year old rubber that is currently on this 72 CB500.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk

[mrmach5]

I would have suspected the steering head bearings had it been a gradual handling change, but this bad habit only appeared after the tire change.
Current pressures are 32 PSI front, 34 PSI rear
I wonder if I could mix and put a K81 on the front and leave the K70 on the rear?

[brewsky]

Recommended pressure for the oem tires was 24-28 Front,  28-36 Rear.

I run mine at 28 Front and 32 Rear.

I always had a "change of feel" (quicker steering) when installing new tires, especially rear, which I attribute to no longer having to have to "ramp up" off the flat spot.

The K70's do have a more squared cross section than the metric sizes.

Maybe try lowering pressure a little and see if there is a difference?

[Stev-o]

Recommended pressure for the oem tires was 24-28 Front...

The K70 is not OEM, I would try raising the pressure to 36...

[brewsky]

Recommended pressure for the oem tires was 24-28 Front...

The K70 is not OEM, I would try raising the pressure to 36...

True enough, but they are similar in design as they are inch sized (roughly the same height and width). The metric sized 404's are shorter and fatter.

Max pressure for the front per Dunlop for the 3.25-19 K70 is listed at 32 psi.

The higher the pressure, the rounder the profile, and hence the quicker the turn, right?

[Stev-o]

Recommended pressure for the oem tires was 24-28 Front...

The K70 is not OEM, I would try raising the pressure to 36...

True enough, but they are similar in design as they are inch sized (roughly the same height and width). The metric sized 404's are shorter and fatter.

Max pressure for the front per Dunlop for the 3.25-19 K70 is listed at 32 psi.

The higher the pressure, the rounder the profile, and hence the quicker the turn, right?

Yes, I think so.  Where did you see the 32psi listed?

[brewsky]

Recommended pressure for the oem tires was 24-28 Front...

The K70 is not OEM, I would try raising the pressure to 36...

True enough, but they are similar in design as they are inch sized (roughly the same height and width). The metric sized 404's are shorter and fatter.

Max pressure for the front per Dunlop for the 3.25-19 K70 is listed at 32 psi.

The higher the pressure, the rounder the profile, and hence the quicker the turn, right?

Yes, I think so.  Where did you see the 32psi listed?

On the Dunlop site...
http://www.dunlopmotorcycletires.com/tire-line/k70/

[Stev-o]

Recommended pressure for the oem tires was 24-28 Front...

The K70 is not OEM, I would try raising the pressure to 36...

True enough, but they are similar in design as they are inch sized (roughly the same height and width). The metric sized 404's are shorter and fatter.

Max pressure for the front per Dunlop for the 3.25-19 K70 is listed at 32 psi.

The higher the pressure, the rounder the profile, and hence the quicker the turn, right?

Yes, I think so.  Where did you see the 32psi listed?

On the Dunlop site...
http://www.dunlopmotorcycletires.com/tire-line/k70/

I don't see max pressure, only max load. 

[brewsky]

Recommended pressure for the oem tires was 24-28 Front...

The K70 is not OEM, I would try raising the pressure to 36...

True enough, but they are similar in design as they are inch sized (roughly the same height and width). The metric sized 404's are shorter and fatter.

Max pressure for the front per Dunlop for the 3.25-19 K70 is listed at 32 psi.

The higher the pressure, the rounder the profile, and hence the quicker the turn, right?

Yes, I think so.  Where did you see the 32psi listed?

On the Dunlop site...
http://www.dunlopmotorcycletires.com/tire-line/k70/

I don't see max pressure, only max load. 

You have to click on the spec tab to get the full chart that includes dimensions, loads, pressures etc.
It won't open on my phone, only on my pc for some reason

[BobbyR]

I would have suspected the steering head bearings had it been a gradual handling change, but this bad habit only appeared after the tire change.
Current pressures are 32 PSI front, 34 PSI rear
I wonder if I could mix and put a K81 on the front and leave the K70 on the rear?

If you do a search on tire pressures you wll see the most experienced riders run at least 34 and more in the front and up to 40 on the rear. The original tire pressures are way too low for the newer tire sidewalls and compounds. 

[Bankerdanny]

I wanted the vintage look but I'm disappointed to hear about the turning performance. It can't be any worse than the rock hard 40-ish year old rubber that is currently on this 72 CB500.

Rick

It's your bike and so your call, but personally I think the vintage look should be reserved for rarely ridden show bikes. For daily riders actual performance should matter more than looks and there is a reason that modern bikes don't use tires with old fashioned tread designs.

the single biggest improvement I made in my 2002 Royal Enfield was replacing the retro style stock tires with modern Avon Roadriders. The ride and handling were so much better it was like I had purchased a completely new bike.

[brewsky]

I would have suspected the steering head bearings had it been a gradual handling change, but this bad habit only appeared after the tire change.
Current pressures are 32 PSI front, 34 PSI rear
I wonder if I could mix and put a K81 on the front and leave the K70 on the rear?

If you do a search on tire pressures you wll see the most experienced riders run at least 34 and more in the front and up to 40 on the rear. The original tire pressures are way too low for the newer tire sidewalls and compounds. 

I agree....higher pressures for newer tire designs (like the 404) but think old recommendation is more appropriate for older design (K70) inch sizes.

I certainly wouldn't recommend running more than the manufacturers max.

I have 404's on my 750 and K70's on my 550, and I like the way they both feel.

[tlbranth]

  The tires I replaced were Dunlop D404's, 100-90-19 on the front, 110-90-18 on the rear. Replaced them with Dunlop K70's for their vintage look, 3.25-19 on the front, 4.00-18 on the rear.
Odd thing is that since I made the change, the bike wants to turn in,, especially at low speed, so does not track at a normal rate.  .........Anyone else experienced this ??

I did the exact opposite.....replaced the old metric sized set (Bridgestone I think) with the same size K70's as you on my '78.

Mine is absolutely neutral in curves and tracks straight as an arrow.

I did replace the steering bearings with tapered at the same time, though.

I have K70's on my CB750 and have no trouble with handling. But I'm not all that picky or discerning. They do wear quickly though and with the inner tubes are a bugger to change so next tires will be something longer wearing - maybe Bridgestone Battleaxe.

[BobbyR]

+1 on the Battleaxes