The Donnelly EMP 700×38 is a high-volume, aggressive tubeless-ready tire designed for demanding off-road and gravel applications. Optimized for maximum grip and puncture resistance, this tire requires proper mounting, sealing, and inflation techniques to ensure reliability and performance. This guide provides detailed, expert-level instructions for installing, adjusting, and maintaining the EMP 700×38 tubeless tires, along with troubleshooting tips and performance optimization strategies.
Tools Required
- Floor pump with high-volume output or air compressor
- Tubeless-compatible rims (pre-taped or ready for tape)
- Tubeless rim tape (25mm width recommended)
- Tubeless valve stems (40–60mm)
- Tire levers (plastic, non-metal)
- Isopropyl alcohol and clean cloth
- Tubeless sealant (60–90ml per tire)
- Valve core remover tool
- Soapy water solution in spray bottle
Preparing the Rim and Tape
To ensure a reliable tubeless seal, the rim bed must be perfectly clean and securely taped.
Start by removing the existing tire and cleaning the rim thoroughly with isopropyl alcohol. Pay close attention to the bead shelf and spoke holes. If your rim is not already taped, apply a high-quality tubeless rim tape. Overlap the tape by at least 10 cm across the valve hole, pressing it firmly into the rim bed with your thumb or a plastic tire lever. Puncture the valve hole cleanly with a sharp object after taping.
Proper tape installation ensures an airtight seal and supports consistent inflation pressures.
Installing the Valve Stem
Insert the tubeless valve through the rim hole from the inside. Secure it tightly with the valve nut on the outside. Hand-tighten the valve nut while pushing the valve base into the tape to compress the rubber base into the rim. This prevents air leaks during inflation and maintains internal pressure.
Use a valve core remover to remove the valve core for initial seating if using an air compressor. Leave the valve core installed if using a tubeless-specific floor pump that delivers sufficient volume.
Mounting the EMP 700×38 Tire
Mount one bead of the tire onto the rim, starting opposite the valve and working your way around. Align the Donnelly logo with the valve for visual consistency. Use your hands to install the bead; avoid using metal levers which could damage the bead or rim.
Once one bead is in place, pour 60–90 ml of sealant into the tire or inject it through the valve stem (if core is removed). Then mount the second bead, again starting opposite the valve and finishing at the valve.
Inspect the bead to ensure it is evenly seated and not twisted or kinked. Rotate the tire gently and tap it on the ground to distribute sealant across the inner casing.
Inflating and Seating the Beads
Inflation must be done rapidly to fully seat the beads against the rim walls. If using an air compressor, quickly inflate the tire while watching and listening for multiple “pops” as the beads snap into place. If using a high-volume floor pump, pump rapidly to build pressure. Initial pressure should be around 40–50 psi to ensure bead seating.
Once seated, reduce pressure to 30–35 psi for riding. Reinstall the valve core if removed earlier and top off pressure if needed.
Check for even bead seating by inspecting the molded bead line around the tire. It should run parallel to the rim edge all around. If it’s uneven, deflate slightly and massage the tire into position, then reinflate.
Sealing the Tire
Shake and rotate the tire in multiple directions to spread the sealant. Lay the wheel flat, then flip it every few minutes to ensure the entire inner casing is coated. This helps seal microscopic pores and any tiny leaks in the bead area.
Let the tire sit for at least 30 minutes horizontally before mounting on the bike. Perform a pressure test over 12 hours. Expect a minor drop of 1–2 psi, but anything more suggests incomplete sealing.
If leaks persist, deflate and reapply sealant, focusing it into the leak zone by shaking and positioning.
Maintenance and Pressure Checks
Tubeless systems are lower-maintenance than tubes, but not maintenance-free.
Check pressure before every ride using a reliable gauge. The optimal pressure for the Donnelly EMP 700×38 is typically between 30–45 psi depending on terrain, rider weight, and ride feel.
Top up sealant every 2–3 months. Remove the valve core and inject 30–60 ml as needed. Check sealant condition periodically by removing the tire or inserting a dipstick. If it’s dry or clumpy, clean out the residue and refresh.
Inspect sidewalls and tread for cuts, embedded debris, and puncture sealant residue. Rotate front and rear tires for even wear.
Troubleshooting Installation Issues
If the beads won’t seat during inflation, verify that:
- The rim tape is fully sealed and not leaking at spoke holes.
- The tire beads are properly aligned within the rim channel.
- The valve core isn’t blocked by dried sealant or improperly tightened.
- The sealant volume is adequate.
If sealant sprays from a specific area during inflation, identify the leak location and reposition the tire while reinflating. In rare cases, adding a small amount of soapy water around the bead can help reduce friction and improve seating.
If a loud air leak occurs from the valve area, ensure the valve stem base is fully compressed against the tape and the nut is snug. A valve core tool can help ensure proper torque without over-tightening.
Optimizing Performance
The Donnelly EMP 700×38 excels in rough terrain, so dialing in the right pressure enhances traction, comfort, and efficiency. Lower pressures improve grip and comfort but increase the risk of burping (air loss) or bottoming out on rim impacts. Higher pressures offer better speed on hardpack but reduce compliance.
For aggressive riders or those carrying extra gear, consider using a tire insert for rim protection and additional bead support.
Pair with wider rims (19–25mm internal width) for better sidewall support and casing shape. This optimizes rolling resistance and handling at lower pressures.
Compatibility with Drivetrain and Frames
The EMP 700×38 fits most modern gravel and endurance frames with clearance for 40mm tires or larger. Always verify with your frame manufacturer’s specs for maximum tire width compatibility.
It is tubeless-ready and optimized for 700c rims with ETRTO 622 compliance. Not compatible with 650b wheel systems.
This tire is not directional and can be mounted in either orientation, though some riders prefer reversing the tread pattern for front vs. rear depending on terrain.
Comparison with Similar Models
Compared to Donnelly’s X’Plor MSO 700×40 or WTB Riddler 700×37, the EMP 700×38 offers superior side lug grip and mud shedding capabilities. It sacrifices a bit of rolling speed but gains predictable traction in technical sections.
The EMP 700×38 has a more aggressive tread pattern than the Panaracer GravelKing SK and performs better in wet, loose, or rooty conditions. For riders prioritizing confidence and control over speed, the EMP is a top-tier choice.
FAQs
What rim width works best with the Donnelly EMP 700×38?
The optimal internal rim width is between 19–25mm to maintain proper casing profile and sidewall support.
How much sealant should I use per tire?
Use 60–90ml per tire, depending on your riding conditions and how frequently you top up.
Can I run this tire with tubes?
Yes, it is tubeless-ready but compatible with tubes if you install a standard 700c tube.
How often should I replace the sealant?
Check every 2–3 months and refresh sealant as needed to maintain air retention and puncture protection.
Is this tire directional?
No, the tread pattern is symmetrical and can be mounted in either orientation without affecting performance.
Why is air leaking from the valve stem?
Ensure the valve nut is tightened and the rubber base is seated flat against the tape. Replace the valve if damaged.