Why is my retrobike slower?

I am very lucky in that my daily cycle to work involves a two mile stretch through the middle of my local trail centre so I get to go biking most days. Now I have two bikes that I alternate between, my Prestige and a Pipedream Sirius (the last of the 26" handrails) and after several months of picking a bike at random each morning and logging my entire ride the Prestige works out about 20 seconds slower per mile. My question to you is why? I've not weighed the bikes but I can't see there being a big difference but it's something I'll check, they both have Hope hubs that I rebuilt with new SKF bearings so I can't see there being much difference with the wheels, for what it's worth I tend to ride the Pipedream with the suspension locked out so it's fully rigid like the Prestige, the only real difference I can spot is the tyres, Conti Race Kings verse Pani Smoke & Darts, would the tyres really drag that much?

Yup!

Race Kings have very low RR for a knobbly.

Aren't race kings pretty much hardpack condition race tyres?

Smoke and dart were just pretty rubbish........

Swap the tyres between the bikes and see what happens...?

Re:

Just to be sure its the tyres, swap the modern bike tyres with the retrobikes tyres and ride the same route a few times, alternating as before. If it is the tyres the results should be opposite. However ride position and the tendency of ride position to affect riding style might also be an issue. I tend to ride flat out on an old XC racer because the low tuck stretched out position just encourages me to go for it

Re:

unconscious bias?

Modern tyres have a lower rolling resistance - you'd notice it straight away if you fit something new to the Orange - I run new on all the old bikes and it just makes them more tolerable.

Smokes are good in damp to sticky, Darts are just terrible whatever.

I seem to remember just about every tyre I used 'back in the day' was utter utter shite with only the Smoke useful with my local sticky clay soil. Ritchey Z-max arent too bad but they seem to have wondered off again.

Nope! Still here:

http://www.ebay.co.uk/itm/BIKE-TYRE-TIR ... xy2HFSX57y

Agreed, tyres are the likeliest answer.

The difference on my P7 from swapping out the Smoke/Darts to Charge Splashback was night and day.

yes, Splashbacks are terrible!

;-P