Isolastics for Race Bikes

We've seen a lot of posts here about isolastic bikes vs. solid mount bikes, with plenty of comments on how terrible the isolastics are for handling. My experiences on the race track with Commandos are that they handle just fine, when properly set up. In defense of them, I thought I'd point out a couple things that seem to have been ignored in these discussions.

All the factory race bikes with Commando engines that I know about had isolastic mounts, including the John Player F750 bikes. That includes the early tube frame racers, the monocoque bikes, and the final tube space frames. They were quite successful racers for the time, given how underpowered they were. Between them they set fast lap times in races, including the IOM, set some lap records, and won plenty of races. They were generally regarded as much better handling than their competitors, but at a serious horsepower disadvantage.

Peter Williams claimed that the monocoque Norton was the best handling bike he'd ever raced. Pretty strong praise for an isolastic bike from a reliable source.

Just to be really clear, I'm not trying to say that a Commando racer handles any better than a good solid mount frame, be it featherbed, Seeley, Rickman, or whatever. But I think they can be made to handle just as well, although they definitely have a different feel to them. The primary benefit I see for a solid mount frame is their weight advantage. Most Commando framed racers are at a significant weight disadvantage to a bike like Kenny Cummings Seeley replica.

Ken

Fascinating! Two types of handling tests a bike, one holding a full lean for some time in a sweeper that lets resonance build up or very fast flicks that shakes on throw down or fling up and may still be shaking by time to flick a new aim. Three ways bikes can respond, fights not to crash holding down or fights and trash to pick back up or just stays put where ever ya leave it w/o resisting lean/radius changes.

Its revelation to me the monocoup retained isolastics as it was said to allow such predicable Delicious effective drifts!~ But I detest drifts as slides me into hazards and reduces or eliminates the harsh acceleration into--out of turns of various radius. Drifts relieve loads and the least time spent sliding the faster ya go around. But drift have some use if you know you are going to loose grip and use that to get bike re-aimed w/o let up till better hook up. BUT there are two types of drifts, flat tracker crossed up flying wide counter steering into the slide only rear sliding and and straight steering not crossed up both tires sliding. Type 1 widens the path, type 2 sharpens the path. Type 1 relieves tire conflict, type 2 piles loads up through chassis. Type 2 makes factory Commandos and stout rigids too nuts for me as tend to tank slap in low side or hi side. I also detest the valve train buzz in moderns sports bikes beside primary vibes. Of course best chassis should make it harder to break loose to drift, but stay hooked up or spin w/o any upset out of line.

Mystery to me if the monocoupe is also too rigid compared to tri linked flexy frame. Mystery to me if mono coup or Seely chassis only brings Cdo into same league as modern rigids on any size tires. Elites try to incorporate some side give in chassis so must be some benefit to distort a bit to handle tire conflicts
My 'research' shows better to have neutral handling so most of chassis loads are same as full up right no matter the lean or radius.

Another important aspect is how athletic pilot must be to control fastest harshest turns and changes. I get worked to a pulp on moderns and Cdos pressing limits, but refreshed relaxed except for the adrenalin high on one of kind Peel. I also think the iso gap setting reveals which set up works best, Peel likes a bit looser than factory gap or tends to vibe on hard leans. So await MacRea 's report on his set up and what he feels upsets limits or not. Kenny both impressed and depressed me he has to use knee to lift Seeley back up when it pogos on rear set peg. Pleased at his fine skill and bike but upset can't further lean to avoid crash to go around faster. Most amazing thing I saw at Barbers was a hinging Indian out lean and out power a 125 on the inside. Kenny says sometime 125's pass him in turns. Something to just enough flexy-ness if it don't keep flexing.