Tires make a difference?

Yes

See this chart http://www.biketechreview.com/tires_old/images/AFM_tire_testing_rev9.pdf

tubes also, latex tubes will roll faster than butyl.

I had a bike that came with Conti Ultra Sports and it would have been cheaper upgrading them the day of purchase versus leaving them on.  Never flatted so much as I did on those tires. 

I ride Continental GP 4000s and those are the only tires I will ride on.  (Other than my race tubulars) Whether it is mental or not, these tires make a difference in my ride (especially in corners).  So, I believe tires absolutely make a difference.

They are just like car tires.  You get what you pay for.  They are the only thing touching the road, so they better be good.

You have gotten good responses so far. The AFM tire chart is a godsend. Its good data that has been verified in field testing out on the road too. Don't let anyone tell you its no good because its just on rollers.

Faster tires are faster because they require less energy to deform as the wheel rolls along the ground. Its got nothing to do with weight or anything else. Latex tubes help a bit for the same reason. Less energy to deform than Butyl.

A great side effect of fast tires is extra comfort too. The downside is less puncture resistance. However if you use a fast tire like the Vittoria EVO CX 320tpi, and ONLY use it for racing, and don't wear it down with too many miles, you will be pretty safe.

The GP4000S is a good compromise tire.

The difference between a BAD tire, like many of the Tufo tubulars, or gatorskins, and a good tire, can be bigger than the difference between a cheap training wheel and a zipp  808.  Many a triathlete has put on zipps with tufo tubulars and wondered why they were slower.

a great tragedy imho

What's the difference between the different models of the Specialized Mondo tires? I noticed there were 5 models. There's a significant difference in the price points in the 5 models and I don't want to pay more than I need to. I struggle on the bike so 15 watts by replacing a tire is great news (if that's indeed the case). 

How about wheel sets? Do they really make a difference? I see a lot of posts referencing Zipp wheelsets.

Also, how do I know when it's time to change my tires?

I don't have the luxury of a separate wheelset and tires for racing. Is it silly to use the faster tires for training?

I forgot to mention, I'm riding a road bike not a TT. I don't know if that impacts the answer to my questions.

Most tires have some sort of wear indicator, like the Contientals have little dimples, once you can't see those any more, its worn out. Also if you notice the wheel is very flat on top instead of round, might be time to go, and once you get flats really easy, time to go!

Yes wheel sets do make a difference. It sounds like you are on a budget, so you can just go with a wheelbuilder wheel cover on the rear, and some good tires, and you won't be giving up too much time to anyone.

I don't like using the same tires to race on as I train on. The fast tires are expensive, don't last as long, and puncture easier. Better to save them for racing so they are in good shape and will be robust for the race.  Should only take a couple minutes to change tires right? =)

I've got some more details on some of your questions in my article on aerodynamic tricks:

http://austintriathlonstore.blogspot.com/2011/02/aerodynamics-victory-by-thousand-cuts.html

Latex tubes don't flat any easier that butyl ones.  The only trick is you MUST!!!!! pull the bead back around the entire perimeter of the wheel, both sides, and be SURE the tube isn't sticking out after installing them. and massage it into place if it is.  You really should always check this with Butyl tubes too but I find that when I'm putting latex tubes in, there is a bit sticking out almost every time.

the latex tubes are kind of 'sticky' so installing them requires more care. if it is installed right, no more flats that butyl. 

Thank you for your input.

Definitely agree with this.  I have a pair of S-Works Mondo Open Tubulars for racing, but use the GP4000s' for every day riding.  They're about middle of the pack for rolling resistance but seem to be very puncture resistant.  I've only had one flat in the past 3 years, and that was installation error with latex tubes. 

Tires make a significant difference.  For wheels, keep an eye on the classifieds here and on Slowtwitch.  You can pick up almost new aero wheels for a fraction of the cost. 

do you have a bike with horizontal dropouts?

you can either adjust the set screws to move the wheel a touch further out, or just do it by hand and make sure the skewer is tight. the tire will wear down after a while then you won't have to bother with that.

I'll adjust the set screws. I didn't know if that was something that needed to be left alone like the derailleur stops. Thanks!

Tires do make a difference.  On my last bike I experimented with a set of 20mm  Vitoria Comp CX 320tpi, latex tubes, pumped to 135psi. On smooth roads the ride was noticebly faster than on my old 23mm Conti GP Triathlon tires & old tubes.  On rough roads its a judgement call between comfort &  speed.

 just don't pump them up soo high. the faster tire is the faster tire on any road. The ideal pressure may change (and for what its worth even on smooth roads, 135psi is probably too high). If a tire is inflated to high that comfort is noticeably affect, then it is also probably slower.  Shaking your body takes energy, that is energy wasted.

Anyone know where I can buy some S-Mondo clinchers on line?  Everywhere I've looked they are sold out.

Thanks,

It's not a stupid question, we've all asked it.  If you have a tube and a tire, that is a clincher.  Most of us have this setup.  With a tubular, the tube and tire are all one piece.

Here is an article explaining it in more detail. http://www.beginnertriathlete.com/cms/article-detail.asp?articleid=979