Tri bike's affect on quads

Short answer: running is more dependent on your hammies and hip flexors.

I second there Bear. Running is more dependent on Hammies and flexors so it is saving your legs. I'm sure you'll see a difference in your run time in your next brick

Unless you have really lousy form, Bear is right.

Being the owner of both a road and tri bike. Both are similar setup (alum frame carbon seat stays/forks/seat post, Full ultegra on road bike, Dura Ace/Ultegra mix tri bike). For a while now i have wondered if there really was any differance. I do most of my training rides/bricks on the tri bike. I had to brick last week using the road bike on a Tuesday then tri bike on the following Thursday. It was not a monumental differance, but I do feel fresher running after being on the tri bike. On the same course and distances for both bricks (20 mile ride/5 mile run), the ride was about the same, but the run was about 3 mins faster using the tri bike. Now to be fair, when I do long rides I do them on the road bike, well I did a 45 mile club ride on Saturday using the tri bike, I was a little faster but over all missed the comfort of the road bike (ex hand positions, more comfortable seat, slightly relaxed geometry...) If I had to only have 1 bike, it would be the road bike. I hope to do a double-not blind test this week. I will do my brick on the tri bike Tuesday and then do same brick Thursday on road bike. I hope this helps.

Thanks for all the feedback/confirmation!

Freeswimmingfish - let me know how the Tuesday and Thursday bricks work out. Do you feel the difference in your run when riding on two different bikes?